An Holter ECG has been recorded for 24 h in 10 couples that had during such time a normal sexual contact. The age varied from 20 to 37 years for women, and 25 to 49 years for men. The average of maximum, medium and minimum rate was major in women than in men. During the initial phase of sexual activity an increase of about 30 beats per minute is verified up to an average rate of 104 b.p.m. without any differences between the two sexes. During realization phase the rate increased ulteriorly. This kind of increase is major and more prolonged in women (137 X 2.8 min.) with respect to men (126 X 2.1 min). The maximum rate observed during sexual contact wasn't superior to the maximum rate observed during the day. We conclude that a normal sexual activity doesn't represent a very pronounced strain, provoking a tachycardia equal to 60-70% of maximum rate of patient and for a short period of time. This should be kept in mind when judging on sexual activity of cardiac patients.