The study consisted of 35 male subjects attending an andrology clinic. The subjects all had poor sperm parameters that could not be attributed to any known medical cause. The objective was to evaluate the relation between various seminal characteristics (volume, total sperm count, sperm viability, proportion of progressively motile sperm, and different sperm morphology) and the blood concentrations of lead, cadmium, mercury, copper, and zinc. The mean blood concentrations of lead, mercury, copper, and zinc were within the normal values; cadmium concentration (1.35 micrograms/L) was much higher than the norms. Asthenozoospermic subjects had significantly (p less than .025) higher blood cadmium levels than normozoospermic subjects. No significant differences were noted between the two groups for mean concentration of mercury, zinc, and copper in blood. Significant correlations were observed between blood cadmium levels and volume of semen, midpiece defects, and immature forms of spermatozoa. High blood cadmium levels may have an effect on spermatogenesis. Possible reasons for the high blood cadmium levels among the subjects are discussed.