The behavioral effects of specific cAMP phosphodiesterase inhibitors (PDE-I) such as rolipram and structurally related compounds were investigated in mice. Selected PDE-I induced a potent dose-dependent decrease in locomotion and in rearing of mice confronted with a free exploratory procedure, these effects being considered as a behavioral sedation. However, in the light/dark choice test especially conceived to reveal disinhibitory and/or anxiolytic action, they did not show obvious effects. These results suggest that the increase of cAMP probably does not account for our previously observed anxiolytic properties of BW A78U, an adenine derivative PDE-I (20).