A crowd is a set of processes that, at some point in time, cooperate to execute some function. The class of functions of interest have the property that they cannot be executed completely in parallel by all of the processes; a partial order is required. By imposing a partial order based on an arbitrary embedding in a balanced binary tree, parallel solutions to these problems can be implemented. A library package for a shared-memory multiprocessor that implements crowd control is described. The package has been implemented on the BBN Butterfly, with performance results that confirm O(log P) expected execution time for crowd control functions using P less than equivalent to 128 processors and constant time functions greater than equivalent to 1 ms in duration.