The cynomolgus monkey (Macaca facicularis) is routinely used in preclinical toxicity testing.For certain drug indications it is important to have sexually mature animals on the studies.For males the presence of sperm in the ejaculate is one of the criteria for determination of sexual maturity.The intent of this study was to evaluate a reliable and repeatable method of semen collection.A total of 10 male cynomolgus monkeys, approximately 5 years of age or older and weighing 4.5 to 6.8 kg, were individually housed in stainless steel cages elevated off the floor, in HEPA-filtered rooms with a 12-h light cycle.