We examined the relationship between lead exposure and fertility among men in a retrospective cohort study. Fertility (1981-1992) of lead-exposed workers was determined from birth certificate information and was compared with that of nonexposed workers. The exposed group consisted of 4256 reproductive-age male workers reported to the New York State Heavy Metals Registry. The comparison group consisted of a random sample of male bus drivers licensed in the state of New York; these men were frequency-matched by age and residence to the men who were exposed to lead. The actual number of births among lead workers was lower than the expected number of births for that group (standardized fertility ratio [SFR] = 0.88; 95% confidence interval [CI] = 0.81-0.95), especially among those who had elevated blood lead levels for longer than 5 years (SFR = 0.43; 95% confidence interval [CI]: = 0.31, 0.59). Even after adjusting for age, race, education, and residence, workers with > 5 years of exposure had reduced likelihood of fathering a child than those with a shorter period of exposure (relative risk, 0.38; 95% CI: 0.23, 0.61). Our study indicates that men with a long duration of lead exposure might have reduced fertility.