In order to determine the role of cadmium and zinc in the very low incidence (10/100,000) of cancer of the prostate, in African blacks which contrasts with the very high incidence (100/100,000) in American blacks, the authors measured the serum and prostatic concentrations of these trace metals in healthy Nigerian men and those with benign prostatic hypertrophy (BPH) and prostatic cancer using atomic absorption spectrophotometric study. The mean plasma zinc concentration of healthy men was 14.9 mumol/l +/- 0.5 SEM, whereas those with BPH and malignant glands were 16.5 mumol/l +/- 0.6 SEM and 11 mumol/l +/- 0.7 SEM, respectively. The mean serum cadmium concentrations were 15.2 mumol/l +/- 0.6 SEM, 15.5 mumol/l +/- 0.7 SEM, and 24.2 +/- 0.9 SEM for normal, BPH, and cancer subjects, respectively. The mean prostatic tissue zinc concentration in normal gland was 12.1 mumol/g +/- 0.8 SEM, BPH 17.9 mumol/g +/- 0.6 SEM, and cancer gland 2.9 mumol/g +/- 0.4 SEM. The mean prostatic tissue cadmium concentration for normal BPH and malignant glands were 3.8 mumol/g +/- 0.6 SEM, 14.6 mumol/g +/- 0.37 SEM. The serum and prostatic tissue values of these trace metals in our controls, BPH, and cancer subjects compare with those from populations with higher prostatic cancer rates. This suggests that these metals do not primarily play any significant role in the reported low incidence rate of prostatic cancer in our community. Furthermore, in control subjects and those with BPH, cadmium/zinc ratio, whether evaluated for serum or prostatic tissue was one or less. In patients with cancer, however, this ratio was always greater than one. The possible clinical use of this ratio to diagnose cancer of the prostate gland and to follow-up such patients needs to be further evaluated through more studies.