The oxygen consumption of the spermatozoa and seminal plasma has been determined polarographically in 115 ejaculates. The mean oxygen consumption of the spermatozoa in samples from healthy men was 4.3 µl O2/108 live cells/hr (SD ± 3.4, range 1.0–12.8; n = 15) and from men with prostatovesiculitis 1.4 µl O2/108 live cells/hr (SD ± 2.5, range 0–8.2; n = 13). The difference was significant (0.01 > p > 0.005). No significant difference was noted between the oxygen consumption of the spermatozoa in specimens from patients with decreased secretory function of the prostate gland (n = 13) or with asthenospermia (n = 25) compared with that in specimens from the healthy subjects. No correlation was found between oxygen consumption of the spermatozoa and various biochemical parameters of the seminal plasma, such as zinc, magnesium, fructose, LDH, and MDH. The mean oxygen consumption of the seminal plasma was 4.4 µl O2/ml/hr (SD ± 1.3, range 1.9–6.0; n = 79). There was no significant difference between samples from the different groups of men.