The effects of maternal cigarette smoking during pregnancy on structural chromosome aberrations were evaluated in peripheral lymphocytes from 239 mothers and their 241 newborns to determine whether smoking during pregnancy, genetic susceptibility, and race are associated with chromosome aberrations including translocations. Demographic information and cigarette smoking data were obtained via questionnaire. There were 119 Caucasian Americans, 118 African Americans, and 2 Asian Americans. The average maternal age was 24.9+/-5.8 (mean+/-S.D.) years. Thirty-nine percent of the Caucasian Americans and 45.4% of the African Americans self-reported that they were active smokers during the index pregnancy. The average number of cigarettes smoked per day was 2.65+/-5.75 and 1.37+/-3.17 for Caucasian and African American mothers, respectively. Peripheral blood lymphocytes from the mother and from the fetal side of the placenta were evaluated for chromosome aberrations by whole chromosome painting. Aliquots from the same blood samples were also used to assess genetic susceptibility with an in vitro bleomycin challenge assay. Spontaneous translocation frequencies in both maternal and newborn lymphocytes were not associated with cigarette smoking, socioeconomic status, or education. The absence of a smoking effect may be attributable to the low level of cigarette usage in these subjects. The average bleomycin-induced damage in the maternal and newborn populations was 0.37+/-0.27 and 0.15+/-0.14 breaks per cell, respectively, a difference that was highly significant (p<0.0001). In newborns there was a positive association between bleomycin sensitivity and the frequencies of aberrations as measured by chromosome painting: p</=0.0007 for dicentrics and fragments, and p</=0.002 for translocations. Caucasian American newborns demonstrated a significant association between dicentrics and fragments as measured by painting, and bleomycin sensitivity (p</=0.0002), but no such association was observed for African American newborns. The results of this study indicate that while differences were observed between African Americans and Caucasian Americans, race does not appear to be a major contributor to chromosome damage in newborns or their mothers. However, peripheral lymphocytes in pregnant women are more susceptible to genetic damage than peripheral lymphocytes in newborns.