The examples that earlier demonstrated the lockfree synchronization mode have only had their captions changed. I think they need lock-unlock calls in them so that users know that these calls are needed and where they are supposed to be placed. pg 22, ln 5: The new op MPI_NO_OP to MPI_Get_accumulate is defined as "It corresponds to the associative function f(a,b) = a; i.e., the current value in the target memory is returned in the result buffer at the origin." Well, "the current value in the target memory is returned in the result buffer at the origin" applies to any op passed to Get_accumulate (by definition). What is special about MPI_NO_OP needs to be mentioned. Therefore, I suggest saying "It corresponds to the associative function f(a,b) = a; i.e., the current value in the target memory is returned in the result buffer at the origin, and no operation is performed on the target buffer." Rajeev