Operant conditioning techniques have been shown to be sensitive to the acute effects of industrial solvents. In the first experiment, five rats trained in a multiple schedule with a fixed-ratio (FR) 10 component and a differential reinforcement of low rates (DRL) 20-sec component, with a time out 60-sec between reinforcement periods, were exposed to 0.25, 0.50, 1 and 2 ml of toluene in the experimental chamber. The effects were dose-dependent, with an increase in rate in the DRL component and a decrease in FR responding. A second experiment assessing the effects of chronic exposure to thinner in the acquisition of a timing behavior in rats showed an impairment in DRL learning after 4, 8 or 16 weeks of exposure to the solvent: however, rats having a resting period did not differ from control animals. Whereas this finding suggests a reversible impairment in the acquisition of a complex behavior, further research is needed to achieve more definitive conclusions.