The role of the perineal muscles in human penile erections is still controversial. The authors investigated surface electromyographic activity of the ischiocavernous muscles together with intracavernous pressure recordings during pressure stimulations of the glans penis. Successive glans stimulations were associated with ischiocavernous muscle contractions and increases in intracavernous pressure reaching two- to fourfold the systolic blood pressure. High correlation coefficients were found between electromyographic and intracavernous pressure amplitudes. Voluntary contractions were accompanied by intracavernous pressure peaks of similar durations, and areas delineated by integrated electromyographic and intracavernous pressure curves showed very high correlation coefficients. Anaesthesia of the dorsal nerve resulted in dramatic reductions of muscle activity and intracavernous pressures in response to glans stimulation. These results suggest that the activity of the muscles in response to pressure stimulation of the glans penis is important to augment rigidity during vaginal penetration and intercourse due to their ability to increase intracavernous pressures.