The transmembrane migration method has permitted quantification of the effect of drugs on human sperm motility. Calcium ionophores and calcium antagonists have paradoxical effects on motility depending on the stage of sperm maturity. Drugs with membrane stabilizing properties inhibit sperm motility. Propranolol, for example, has been shown to have contraceptive activity when administered intra-vaginally. Pharmacokinetic studies have shown that the systemic availability of vaginally administered propranolol is markedly greater than after oral administration. Seminal fluid concentrations of propranolol after oral administration are similar to those in plasma, but cervicovaginal mucus concentrations are much higher, and residence times much longer. The clinical consequences of these observations await elucidation.