Semen was collected from adult male Macaca fascicularis using a rectal probe for electro-ejaculation. The effect on sperm motility of varying semen extender egg yolk concentration, pH, glycerol concentration, and equilibration times of sperm with glycerol was examined. No significant difference was observed between motilities at extender egg yolk concentrations of 10% to 40%. Progressive motility was significantly greater at pH 7.2 and 8.0 than at 5.8, 6.5, and 8.7 (p less than 0.05). Glycerol concentrations of 7% and 10% yielded optimum progressive motility after freezing. A 1-minute equilibration of semen in extender containing glycerol resulted in greater sperm motility after freezing than did equilibration for 25 or 45 minutes.