Sprague-Dawley rats were used to investigate the effects of neonatal ethanol (ETOH) and nicotine (NIC) exposure on activity levels in preweanling offspring. Male and female pups received daily oral intubations of ethanol ((ETOH) 5 g/kg/day), nicotine ((NIC) 12 mg/kg/day), ethanol and nicotine ((ETOH+NIC) 5 g/kg/day+12 mg/kg/day) or isocaloric maltose (control) on either postnatal days (PND) 1-7 or PND 8-14. A non-treated control group was also included. Peak blood ethanol concentrations (BECs) measured in a separate subset of animals ranged from 167 and 344 mg/dl depending upon neonatal treatment and period of exposure. Subjects were tested in an open field apparatus on PND 19-21. Animals exposed to ETOH or ETOH+NIC on PND 1-7 were hyperactive relative to the other treatment groups. In contrast, animals exposed to NIC or ETOH+NIC during PND 8-14 were hypoactive relative to other treatment groups. Males appeared more sensitive than females on measures of anxiety (distance traveled in the center of the open field) but this also varied dependent on neonatal treatment and period of exposure. These findings suggest that the third trimester is a critical period for ETOH and NIC effects on offspring activity although the pattern of effects on activity are different depending on when drug exposure occurred during the neonatal period.