In this paper a hardware/software system is described which permits the use of the Radio Shack TRS-80 Model I as a tachistoscope in perceptual-cognitive research. Hardware requirements and configuration, problems in developing software routines to handle reaction and stimulus timing using the TRS-80, and the development of a routine for tachistoscopic stimulus display using the TRS-80 are discussed. The limitations of the TRS-80 as a tachistoscope are outlined and ways to overcome those limitations are presented. Accompanying the text are an 8-item reference list, a block diagram of the hardware configuration for using the TRS-80 as a tachistoscope, a figure illustrating the assembly language tachistoscopic display and reaction time routine, and a figure illustrating portions of the BASIC program for tachistoscopic display. (Author/JL)