We tried to make a successful collection of semen by human fingers, using ten African green monkeys (Cercopithecus aethiops) aged from 5-7 years, which were bred and reared at Tsukuba Primate Center for Medical Science. Under anesthesia, the animals were laid side way and their penis were gently stimulated by fingers. Semen was successfully obtained from five animals aged 6-7 years, but it was impossible to collect semen from the remaining five animals aged 5 years. It took only 5-15 seconds from the beginning of stimulation to the end of semen collection. The volume of semen collected, the number of spermatozoa and spermatozoal motility rate averaged 1.5 ml, 3.1 x 10(8)/ml, and 46%, respectively.