This study was undertaken to determine whether spermatozoa from the caput of the bovine epididymis glycolyze at lower rates than those from the cauda and, if so, what factors might be involved in the activation of glycolysis during epididymal maturation. Bovine caput sperm glycolyze at approximately one-third the rate of caudal sperm and convert a lower percentage of the utilized glucose to lactate. Comparison of glycolytic rates between these cell types requires kinetic, rather than end-point, analysis. This is so because both glucose utilization and lactate formation in caput sperm are characterized by a distinct lag phase of some 5-mm duration while changes in these parameters in caudal sperm describe hyperbolic plots.