The design of an automatic electronic blood pressure recording device is described. This device, which applied pressure only slightly higher than the systolic pressure of the subject, is programed to record the Korotkoff sounds while the occlusion cuff is being inflated. The system may be programed to monitor blood pressure at any predetermined rate from intervals of one minute to several minutes, or it may be initiated manually. Proper design of circuitry for maximum signal-to-noise ratio required a knowledge of the frequency range of the complex Korotkoff sound waveform. This information was obtained by recording the K sounds from four subjects and analyzing the waveforms for energy content vs. frequency. These data are also presented.