We conducted a retrospective study on time to pregnancy among the wives of men biologically monitored for lead to assess whether paternal occupational exposure to inorganic lead is associated with decreased fertility. After three mailings, 554 (72.2%) wives of the monitored men participated. The final study population consisted of 502 couples who did not use contraception at the beginning of the pregnancy. We assessed lead exposure from blood lead measurements and from questionnaires completed by the men. We calculated the relative fecundability density ratios with discrete proportional hazards regression. The fecundability density ratios, adjusted for potential confounders, were 0.92 [95% confidence interval (95% CI) = 0.73-1.16], 0.89 (95% CI = 0.66-1.20), 0.58 (95% CI = 0.33-0.96), and 0.83 (95% CI = 0.50-1.32) for blood lead categories 0.5-0.9, 1.0-1.4, 1.5-1.8, and > or =1.9 micromol/L, respectively, as compared with <0.5 micromol/L. The findings provide limited support for the hypothesis that paternal exposure to lead is associated with decreased fertility.