Organochlorine (OC) plasma levels and their dietary and reproductive determinants were investigated in 64 pregnant women from Rio de Janeiro, Brazil. Prenatal exposure of newborns was evaluated in a subset of these women in which umbilical cord blood was analyzed. To assess the influence of dietary factors on OC levels, a semiquantitative food frequency questionnaire was completed by participants. Nondietary determinants were investigated through a general questionnaire that addressed reproductive history, lifestyle, and social-demographic characteristics. Both women and their newborns had detectable but low levels of OCs. The most frequently detected compound was p,p'-DDE, the main metabolite of p,p'-DDT. This compound was found in 97% of the women who participated in the study and in 67% of the umbilical cord blood samples, with levels ranging from 0.161 to 8.03ppb and from 0.320 to 1.06ppb, respectively. Among the OCs detected, only p,p'-DDE showed any correlation with dietary and nondietary factors. There was a positive correlation between maternal p,p'-DDE and the consumption of fish (Pearson r=0.38,P=0.002) and chicken (Pearson r=0.26, P=0.042). The correlation between pork consumption and p,p'-DDE exhibited an inverse relationship (Pearson r=-0.25,P=0.052). Parity was the only nondietary factor that showed a significant correlation (Pearson r=-0.36,P=0.004). The main determinants of p,p'-DDE levels in this group of women were fish consumption and parity, together explaining 28% of the variance (P<001), in a multivariate model.