A heart rate biofeedback system consisting of a JPR 12 minicomputer (12 bit, 4 K), of input devices (an electronic circuit triggered by the EEG R-waves or a photoelectric ear lobe pulse detector and of output devices (a feedback indicator of successful or unsuccessful heart rate control during the preceding time interval, the teletype and the paper tape punch) is described. The actual heart rate is measured and compared with levels differing from the average by a preselected number of pulses/min. When a preset criterion is met, the levels are shifted automatically. In control session shuffled data from the preceding experimental session are used for feedback.