Neurotoxicology 15(3): 621-624, 1994. In the present study we have investigated the effects of toluene exposure (80 ppm, 4 weeks, 5 day/week, 6 h/day) on the serum levels of prolactin, and elaborated our earlier findings about persistent effects of toluene exposure on apomorphine-induced (1 mg/kg, s.c.) locomotor activity. We found that the serum levels of prolactin were increased by 67% in the toluene-exposed rats, as analyzed 17 days after the last exposure. The locomotor activity counts of the control rats were not normally distributed before log-transformation, since most rats showed a low level of activity and only a few showed a very high activity level. The toluene-exposed rats showed a higher level of apomorphine-induced locomotion and motility but not rearing, as analyzed 17 days after the last exposure, whereas spontaneous locomotor activity was unaffected. These results indicate that subacute exposure to 80 ppm of toluene causes persistent impairments in dopamine-mediated neurotransmission.