In the presence of glucose, respiration and the levels of citric acid cycle intermediates in washed human spermatozoa are low. Citrate levels are not markedly increased by pyruvate, lactate or acetate, nor do these compounds increase respiration. Succinate, which is oxidized at high rates, increases citrate levels about fourfold; however, the increased respiration is attributed to the succinate—fumarate conversion alone and not to a general stimulation of the citric acid cycle. The addition of succinate, malate, or fumarate to sperm suspensions containing pyruvate increases citrate levels 50- to 100-fold, markedly stimulates α-ketoglutarate formation, decreases glycolysis and almost doubles the rate of pyruvate utilization. The increased rates of the synthesis of citrate and other intermediates of the citric acid cycle are not accompanied by increased rates of respiration. These data argue for the presence of a powerful pyruvate dismutation pathway in human spermatozoa in which lactic dehydrogenase competes successfully for the reducing equivalents generated by pyruvate oxidation and argues against the idea that oxidation in spermatozoa is limited by substrate entry into the citric acid cycle.