Abstract Nicotine was administered to adult female rats in drinking water starting 6 weeks before mating and continuing throughout pregnancy. The litters were cross-fostered to control dams at birth. Prenatal nicotine treatment reduced both the number of male rats born and the male birth weight. Female offspring were not significantly affected. Rearing activity was reduced in male but not female offspring either when tested over a 24 hour period in a home cage environment or during a 10 minute exposure in an open field. Horizontal locomotor activity was reduced only during the first 5 minutes in the open field and again the effect was found only in the males. Baseline plasma corticosterone levels were reduced in both male and female offspring but there was no effect on stress-elevated corticosterone levels.