There is a growing interest in the potential benefits to be obtained from closed-loop control of drug infusion [1—5]. The most widely available infusion pump which is specifically designed for control by computer is the 929 volumetric infusion pump produced by Imed. The increasing availability of microcomputers suggests that they will be used more frequently to control such pumps. However, difficulties can arise when the attempt is made to establish communication between the computer and the pump [6]and a method employed for this purpose is described in this article. The aim was to provide a simple method of conducting the required communication between the computer and the pump using a high—level language. The commands specified in the high—level Language are passed to a machine—code subroutine which organizes transmission to and receives data from the pump.