The possible effect of environmental pollution on fetal growth was examined in 3,231 consecutively liveborn single infants (>/=37 weeks' gestation) of Caucasian parents born between 1986 and 1988. The parents lived in an industrial area or in less polluted urban and rural residential areas. Information about lifestyle, health, and work exposures was collected from the parents. A significantly lower arithmetic mean birth weight was observed for newborns in the industrial residential area (3,517 g, SD, 482), compared with the urban (3,592 g, SD 495) and rural (3,618 g, SD 517) areas (P < 0.05). Even controlling for gestational age, sex, parity, maternal smoking habits, and social class, residential area still had a significant effect on birth weight. Among other factors examined, only maternal psychological stress at work had a significant effect on birth weight. If the observed association reflects a causal relationship, birth weight may represent a potential outcome parameter for surveillance of effects on humans of environmental exposures.