Because of their roles in motility regulation and energy transport, calcium and creatine phosphate were examined for their effects on sperm motility and velocity in specimens of normal donors. Semen or migrated sperm fractions were incubated with of 1 mmol of calcium, 5 mmol magnesium, and 10 mmol of creatine phosphate (n = 28) or in the presence of 4 mumol of Verapamil, calcium, and creatine phosphate (n = 10). The samples were subjected to multiple exposure photography (four picture frames of two different drops) at 0, 1, 4, or 5 and at 10 hours and sperm motility and velocity were analyzed. In both calcium and calcium-creatine phosphate conditions, sperm motility and velocity were significantly increased, compared with control values (P = between less than 0.001 and 0.05). Sperm motility declined following Verapamil exposure, but the motility values remained at the level of the control in the presence of additional calcium or creatine phosphate. The effects of calcium and creatine phosphate take place rapidly; within 1 minute all improvements in sperm velocity and motility are fully achieved. There is no loading effect of calcium, and when the sperm is transferred into media without the additional calcium, the velocity decreased to that of the initial control value. Magnesium alone had no effect on motility or velocity. These experiments indicate that calcium or creatine phosphate can support sperm motility and velocity at a significantly increased level. Thus the addition of calcium or creatine phosphate to the insemination media may enhance the fertilizing capacity of sperm during in vitro fertilization or gamete intrafallopian transfer procedures.