To determine if increased lead absorption was associated with sperm count suppression or perterbation of the hypothalamopituitary system, we compared battery workers (N = 18), who were exposed to high airborne lead levels, with cement workers (N = 18), who were exposed to ambient lead levels. Blood lead, urinary lead, semen lead, and zinc protoporphyrin concentrations were markedly elevated (p less than .001) in battery workers. Battery workers had a significantly shifted (p less than .025) frequency distribution of sperm count (median count, 45 vs. 73 X 10(6) cells/cc, respectively). There were no significant differences between the two groups in mean follicle-stimulating hormone, testosterone, prolactin, luteinizing hormone, or total neutral 17-ketosteroid levels. Potential confounding factors (alcohol, cigarette, and coffee consumption, frequency of intercourse, and days of abstinence prior to semen donation) were not significantly different between the two groups. These results suggest a direct toxic effect of increased lead absorption on sperm production or transport in man.