Contamination of fish in the Great Lakes generated three surveys assessing polychlorinated biphenyls (PCB) serum concentration in Michigan anglers: 1973 to 1974, 1979 to 1982, and 1989 to 1991. This cohort provided 1177 individuals with PCB determinations. In 2000, we conducted telephone interviews with parents on their children's birth characteristics. We estimated the sex odds ratio for parental PCB and dichlorodiphenyl dichloroethene concentrations using generalized estimation equations. We identified 208 offspring, within 101 families, born after 1963, with paternal measurements of both PCB and dichlorodiphenyl dichloroethene. When controlling for maternal exposure and parental dichlorodiphenyl dichloroethene, the sex odds ratio was increased if paternal PCB concentrations exceeded 8.1 micrograms/L (sex ratio, 2.29; 95% confidence interval, 1.11 to 4.74). Thus, paternal exposure was linked to a higher proportion of male offspring. These findings are opposite those reported for the Seveso study and are in accordance with those for dioxin exposure in the American veterans study.