A cassette recorder (Medilog miniature analogue tape recorder) initially developed for prolonged recording of ECG and EEG has been adapted for monitoring physiological change during sexual response. The recorder is small, portable, and reliable. Recording can be done by the subject in private. By avoiding the problem of invasion of privacy, it may prove practical to obtain data from patients when information about their ability to cope with the stress of sex response is neeeded for medical counseling. Additionally, a larger population than would ordinarily be available for sex research may become available for study. Tracings from a recording of EEG, ECG, and vaginal photoplethysmography during sex response are presented.