diff --git a/ompi/communicator/comm_cid.c b/ompi/communicator/comm_cid.c
index 9e25217cb6..7eded4e9fc 100644
--- a/ompi/communicator/comm_cid.c
+++ b/ompi/communicator/comm_cid.c
@@ -9,6 +9,7 @@
  *                         University of Stuttgart.  All rights reserved.
  * Copyright (c) 2004-2005 The Regents of the University of California.
  *                         All rights reserved.
+ * Copyright (c) 2006      University of Houston. All rights reserved.
  * $COPYRIGHT$
  * 
  * Additional copyrights may follow
@@ -30,6 +31,7 @@
 #include "ompi/mca/coll/base/base.h"
 #include "orte/mca/rml/rml.h"
 #include "ompi/request/request.h"
+#include "ompi/runtime/mpiruntime.h"
 
 #if defined(c_plusplus) || defined(__cplusplus)
 extern "C" {
@@ -41,6 +43,8 @@ extern "C" {
  * and a bridge-comm (intercomm-create scenario).
  */
 
+static int cid_block_start = 28;
+
 typedef int ompi_comm_cid_allredfct (int *inbuf, int* outbuf, 
                                      int count, struct ompi_op_t *op, 
                                      ompi_communicator_t *comm,
@@ -104,7 +108,6 @@ static opal_mutex_t ompi_cid_lock;
 #endif  /* OMPI_HAVE_THREAD_SUPPORT */
 static opal_list_t ompi_registered_comms;
 
-
 int ompi_comm_nextcid ( ompi_communicator_t* newcomm, 
                         ompi_communicator_t* comm, 
                         ompi_communicator_t* bridgecomm, 
@@ -112,14 +115,9 @@ int ompi_comm_nextcid ( ompi_communicator_t* newcomm,
                         void* remote_leader,
                         int mode, int send_first )
 {
-
-    int nextlocal_cid;
-    int nextcid;
-    int done=0;
-    int response=0, glresponse=0;
+    int nextcid, block;
+    int global_block_start;
     bool flag;
-    int start=ompi_mpi_communicators.lowest_free;
-    int i;
     
     ompi_comm_cid_allredfct* allredfnct;
 
@@ -146,79 +144,149 @@ int ompi_comm_nextcid ( ompi_communicator_t* newcomm,
             break;
         }
 
-
-    OPAL_THREAD_LOCK(&ompi_cid_lock);
-    ompi_comm_register_cid (comm->c_contextid);
-    OPAL_THREAD_UNLOCK(&ompi_cid_lock);
-
-    while (!done) {
-	/**
-	 * This is the real algorithm described in the doc 
-	 */
-
+    /**
+     * In case multi-threading is enabled, we revert to the old algorithm
+     * starting from cid_block_start
+     */
+    if (MPI_THREAD_MULTIPLE == ompi_mpi_thread_provided) {
+	int nextlocal_cid;
+	int done=0;
+	int response=0, glresponse=0;
+	int start=ompi_mpi_communicators.lowest_free;
+	int i;
+	
 	OPAL_THREAD_LOCK(&ompi_cid_lock);
-	if (comm->c_contextid != ompi_comm_lowest_cid() ) {
-	    /* if not lowest cid, we do not continue, but sleep and try again */
-	    OPAL_THREAD_UNLOCK(&ompi_cid_lock);
-	    continue;
-	}
+	ompi_comm_register_cid (comm->c_contextid);
 	OPAL_THREAD_UNLOCK(&ompi_cid_lock);
-
-
-	for (i=start; i < mca_pml.pml_max_contextid ; i++) {
-            flag=ompi_pointer_array_test_and_set_item(&ompi_mpi_communicators, i, comm);
-            if (true == flag) {
-                nextlocal_cid = i;
-                break;
-            }
-        }
-
-        (allredfnct)(&nextlocal_cid, &nextcid, 1, MPI_MAX, comm, bridgecomm,
-                     local_leader, remote_leader, send_first );
-        if (nextcid == nextlocal_cid) {
-            response = 1; /* fine with me */
-        }
-        else {
-            ompi_pointer_array_set_item(&ompi_mpi_communicators, 
-                                        nextlocal_cid, NULL);
-
-            flag = ompi_pointer_array_test_and_set_item(&ompi_mpi_communicators, 
-                                                         nextcid, comm );
-            if (true == flag) {
-                response = 1; /* works as well */
-            }
-            else {
-                response = 0; /* nope, not acceptable */
-            }
-        }
-        
-        (allredfnct)(&response, &glresponse, 1, MPI_MIN, comm, bridgecomm,
-                         local_leader, remote_leader, send_first );
-        if (1 == glresponse) {
-            done = 1;             /* we are done */
-            break;
-        }
-	else if ( 0 == glresponse ) {
-	    if ( 1 == response ) {
-		/* we could use that, but other don't agree */
-		ompi_pointer_array_set_item(&ompi_mpi_communicators, 
-					    nextcid, NULL);
+	
+	while (!done) {
+	    /**
+	     * This is the real algorithm described in the doc 
+	     */
+	    
+	    OPAL_THREAD_LOCK(&ompi_cid_lock);
+	    if (comm->c_contextid != ompi_comm_lowest_cid() ) {
+		/* if not lowest cid, we do not continue, but sleep and try again */
+		OPAL_THREAD_UNLOCK(&ompi_cid_lock);
+		continue;
+	    }
+	    OPAL_THREAD_UNLOCK(&ompi_cid_lock);
+	    
+	    
+	    for (i=start; i < mca_pml.pml_max_contextid ; i++) {
+		flag=ompi_pointer_array_test_and_set_item(&ompi_mpi_communicators, 
+							  i, comm);
+		if (true == flag) {
+		    nextlocal_cid = i;
+		    break;
+		}
+	    }
+	    
+	    (allredfnct)(&nextlocal_cid, &nextcid, 1, MPI_MAX, comm, bridgecomm,
+			 local_leader, remote_leader, send_first );
+	    if (nextcid == nextlocal_cid) {
+		response = 1; /* fine with me */
+	    }
+	    else {
+		ompi_pointer_array_set_item(&ompi_mpi_communicators, 
+					    nextlocal_cid, NULL);
+		
+		flag = ompi_pointer_array_test_and_set_item(&ompi_mpi_communicators, 
+							    nextcid, comm );
+		if (true == flag) {
+		    response = 1; /* works as well */
+		}
+		else {
+		    response = 0; /* nope, not acceptable */
+		}
+	    }
+	    
+	    (allredfnct)(&response, &glresponse, 1, MPI_MIN, comm, bridgecomm,
+                         local_leader, remote_leader, send_first );
+	    if (1 == glresponse) {
+		done = 1;             /* we are done */
+		break;
+	    }
+	    else if ( 0 == glresponse ) {
+		if ( 1 == response ) {
+		    /* we could use that, but other don't agree */
+		    ompi_pointer_array_set_item(&ompi_mpi_communicators, 
+						nextcid, NULL);
+		}
+		start = nextcid+1; /* that's where we can start the next round */
 	    }
-	    start = nextcid+1; /* that's where we can start the next round */
 	}
+	
+	/* set the according values to the newcomm */
+	newcomm->c_contextid = nextcid;
+	newcomm->c_f_to_c_index = newcomm->c_contextid;
+	ompi_pointer_array_set_item (&ompi_mpi_communicators, nextcid, newcomm);
+	
+	OPAL_THREAD_LOCK(&ompi_cid_lock);
+	ompi_comm_unregister_cid (comm->c_contextid);
+	OPAL_THREAD_UNLOCK(&ompi_cid_lock);
+	
+	return (MPI_SUCCESS);
+    }
+
+     /**
+      * In case the communication mode is INTRA_OOB or INTAR_BRIDGE, we use the 
+      * highest-free algorithm
+      */
+    if ( OMPI_COMM_CID_INTRA_OOB == mode || OMPI_COMM_CID_INTRA_BRIDGE == mode) {
+	(allredfnct)(&cid_block_start, &global_block_start, 1, 
+		     MPI_MAX, comm, bridgecomm,
+		     local_leader, remote_leader, send_first );
+	cid_block_start = global_block_start;
+	nextcid = cid_block_start;
+	cid_block_start = cid_block_start + 1;
+    }
+    else {
+	flag=false;
+	block = 0;
+	if( 0 == comm->c_contextid ) {
+	    block = OMPI_COMM_BLOCK_WORLD;
+	}
+	else {
+	    block = OMPI_COMM_BLOCK_OTHERS;
+	}
+
+	while(!flag) {
+	    /**
+	     * If the communicator has IDs available then allocate one for the child
+	     */
+	    if(MPI_UNDEFINED != comm->c_id_available && 
+	       MPI_UNDEFINED != comm->c_id_start_index &&  
+	       block > comm->c_id_available - comm->c_id_start_index) {
+		nextcid = comm->c_id_available;
+		flag=ompi_pointer_array_test_and_set_item (&ompi_mpi_communicators,
+							   nextcid, comm);
+	    }
+	    /**
+	     * Otherwise the communicator needs to negotiate a new block of IDs
+	     */
+	    else {
+		(allredfnct)(&cid_block_start, &global_block_start, 1, 
+			     MPI_MAX, comm, bridgecomm,
+			     local_leader, remote_leader, send_first );
+		cid_block_start = global_block_start;
+		comm->c_id_available = cid_block_start;
+		comm->c_id_start_index = cid_block_start;
+		cid_block_start = cid_block_start + block;
+	    }
+	}
+	
+	comm->c_id_available++;
     }
-    
     /* set the according values to the newcomm */
     newcomm->c_contextid = nextcid;
     newcomm->c_f_to_c_index = newcomm->c_contextid;
     ompi_pointer_array_set_item (&ompi_mpi_communicators, nextcid, newcomm);
 
-    OPAL_THREAD_LOCK(&ompi_cid_lock);
-    ompi_comm_unregister_cid (comm->c_contextid);
-    OPAL_THREAD_UNLOCK(&ompi_cid_lock);
-
     return (MPI_SUCCESS);
+
 }
+
 /**************************************************************************/
 /**************************************************************************/
 /**************************************************************************/
diff --git a/ompi/communicator/comm_init.c b/ompi/communicator/comm_init.c
index e812cb1806..f7957b1fa8 100644
--- a/ompi/communicator/comm_init.c
+++ b/ompi/communicator/comm_init.c
@@ -9,6 +9,7 @@
  *                         University of Stuttgart.  All rights reserved.
  * Copyright (c) 2004-2005 The Regents of the University of California.
  *                         All rights reserved.
+ * Copyright (c) 2006      University of Houston. All rights reserved.
  * $COPYRIGHT$
  * 
  * Additional copyrights may follow
@@ -77,6 +78,8 @@ int ompi_comm_init(void)
     ompi_group_increment_proc_count (group);
 
     ompi_mpi_comm_world.c_contextid    = 0;
+    ompi_mpi_comm_world.c_id_start_index = 4;
+    ompi_mpi_comm_world.c_id_available = 4;
     ompi_mpi_comm_world.c_f_to_c_index = 0;
     ompi_mpi_comm_world.c_my_rank      = group->grp_my_rank;
     ompi_mpi_comm_world.c_local_group  = group;
@@ -108,6 +111,8 @@ int ompi_comm_init(void)
 
     ompi_mpi_comm_self.c_contextid    = 1;
     ompi_mpi_comm_self.c_f_to_c_index = 1;
+    ompi_mpi_comm_self.c_id_start_index = 20;
+    ompi_mpi_comm_self.c_id_available = 20;
     ompi_mpi_comm_self.c_my_rank      = group->grp_my_rank;
     ompi_mpi_comm_self.c_local_group  = group;
     ompi_mpi_comm_self.c_remote_group = group;
@@ -257,6 +262,8 @@ static void ompi_comm_construct(ompi_communicator_t* comm)
     comm->c_f_to_c_index = MPI_UNDEFINED;
     comm->c_name[0]      = '\0';
     comm->c_contextid    = MPI_UNDEFINED;
+    comm->c_id_available = MPI_UNDEFINED;
+    comm->c_id_start_index = MPI_UNDEFINED;
     comm->c_flags        = 0;
     comm->c_my_rank      = 0;
     comm->c_cube_dim     = 0;
diff --git a/ompi/communicator/communicator.h b/ompi/communicator/communicator.h
index d19f659fb7..3da5bed840 100644
--- a/ompi/communicator/communicator.h
+++ b/ompi/communicator/communicator.h
@@ -10,6 +10,7 @@
  * Copyright (c) 2004-2005 The Regents of the University of California.
  *                         All rights reserved.
  * Copyright (c) 2006      Cisco Systems, Inc.  All rights reserved.
+ * Copyright (c) 2006      University of Houston. All rights reserved.
  * $COPYRIGHT$
  * 
  * Additional copyrights may follow
@@ -83,6 +84,13 @@ OMPI_DECLSPEC OBJ_CLASS_DECLARATION(ompi_communicator_t);
 #define OMPI_COMM_CID_INTRA_BRIDGE 0x00000080
 #define OMPI_COMM_CID_INTRA_OOB    0x00000100
 
+/**
+ * The block of CIDs allocated for MPI_COMM_WORLD
+ * and other communicators
+ */
+#define OMPI_COMM_BLOCK_WORLD      16
+#define OMPI_COMM_BLOCK_OTHERS     8
+
 OMPI_DECLSPEC extern ompi_pointer_array_t ompi_mpi_communicators;
 
 struct ompi_communicator_t {
@@ -95,6 +103,11 @@ struct ompi_communicator_t {
     uint32_t                  c_flags; /* flags, e.g. intercomm,
                                           topology, etc. */
 
+    int c_id_available; /* the currently available Cid for allocation 
+			   to a child*/
+    int c_id_start_index; /* the starting index of the block of cids 
+			     allocated to tthis communicator*/
+
     ompi_group_t        *c_local_group;
     ompi_group_t       *c_remote_group;
 
@@ -344,7 +357,6 @@ struct ompi_communicator_t {
                             int mode,
                             int send_first);
 
-
     /**
      * shut down the communicator infrastructure.
      */