Tobacco smoke was administered to male and female mice of four inbred strains and two lines selectively bred for high activity (HA) or low activity (LA) in an open field. Administration occurred during 14 daily 10-min pretreatment sessions in a box filled with smoke from a nonfiltered cigarette (2 mg nicotine/ cigarette; average density, 750 ppm carbon monoxide). When open-field activity was subsequently measured in the absence or presence of smoke (average density, 150 ppm carbon monoxide), pretreated mice had significantly lower activity scores than controls. Comparisons of open-field activity scores under smoke-present and smoke-absent conditions revealed that effects of this acute exposure were dependent upon genotype: C3H/2Ibg activity was almost tripled in the presence of smoke; DBA/2Ibg activity was increased; but HA, LA, and C57BL/6Ibg activity scores were depressed. As measured by open-field activity, development of tolerance to the effects of acute exposure to tobacco smoke after chronic pretreatment was also genotype-dependent. Significant genotypic differences were found for nicotine remaining in liver, brain, and blood samples when mice were sacrificed 2.5 or 5 min after a weight-specific injection of radiolabeled nicotine. Tissue nicotine levels were also related to sex, time after injection, and pretreatment interactions with genotype. Strong positive correlations were found between the measures of brain and liver levels at 5 min after injection and the behavioral measure of open-field activity under the smoke-present condition.