A simple, flexible, and relatively inexpensive microcomputer‐controlled shutter system intended, principally, for use with molecular‐beam epitaxial reactors is described. Eight pneumatic shutters, each one controlling the molecular‐beam emission of a corresponding effusion cell, can be operated in any combination simultaneously or sequentially. Such a system has been built and is being used to grow heterojunction and superlattice structures of binary and ternary III‐V alloys.