Platelet-activating factor is a naturally occurring molecule that does not appear to cause the detrimental effects to sperm as have been reported for other synthetic stimulatory agents. Incubation of freeze-thawed sperm with low motility with PAF at concentrations greater than or equal to 1.0 microM significantly improved a number of motion parameters (% motility, VSL and LIN). Optimal incubation conditions for PAF were defined at 1 hour and at 25 degrees C. The success of assisted reproductive techniques employing cryopreserved sperm with poor motility may be enhanced by stimulation protocols employing PAF.