Nicotine, a cognition enhancer and a drug of abuse, exerts its central actions through neuronal nicotinic acetylcholine receptors which show sexual dimorphism. This study tested the effects of nicotine on active avoidance learning in male and female rats. Three month-old Sprague-Dawley rats received varying doses of nicotine (0.2, 0.4 and 0.6 mg/kg) or saline s.c. before active avoidance learning trials (15 trials/day) for a period of 5 days. Behavioural testing was continued after the termination of nicotine treatment once a week for four weeks. Nicotine improved acquisition of active avoidance learning in a dose-dependent manner. fn male rats nicotine was active at all doses tested whereas, in females, learning performance deteriorated at a dose of 0.6 mg/kg. In conclusion, nicotine pre-treatment affects active avoidance in a sexually dimorphic and dose-dependent manner.