The behavioral performances of adult mice exposed to sub-acute doses of benzo(a)pyrene (B(a)P) were monitored in tests related to learning and memory (Y maze and Morris water maze), locomotor activity (open-field test) and motor coordination (Locotronic apparatus). At low doses (0.02 and 0.2mg/kg), B(a)P impaired short-term learning and spatial memory performance in the Y maze and in the Morris water maze tests. Surprisingly, in the Y maze, the performances of animals exposed to the highest dose of B(a)P (200mg/kg) were quite similar to those of control animals. Hyperactivity/hyperarousal observed in both tests at this dose and attributed to an anxiolytic-like effect of B(a)P may have blurred the learning deficit in these mice faced with a new situation. These deficits seem to be unrelated to motor impairments because B(a)P had no effect on locomotor activity and motor coordination. We demonstrated that sub-acute exposure to B(a)P in adult mice also modulates gene expression of NMDA-R1 subunit in brain areas highly involved in cognitive function like the hippocampus, suggesting a relationship between the expression of functional NMDA-R1 mRNA, impairment of short-term and spatial memory and the B(a)P exposure levels.