The selectivity of Ro 15-4513 in reversing the actions of sedative-hypnotic drugs was examined. The motor impairment induced by i.p. administration of 1.8 g/kg of ethanol was partially reversed by doses of Ro 15-4513 ranging from 2-8 mg/kg. Antagonism of the similar effect induced by 20 mg/kg of pentobarbital was observed only at the 8 mg/kg dose of Ro 15-4513. Treatment with 4 mg/kg of Ro 15-4513 shifted the dose-effect curve for motor impairment by ethanol to the right but did not affect the corresponding curve for pentobarbital. Ro 15-4513 also increased the onset latency and shortened the duration of sleep time induced by ethanol but not by pentobarbital. Blood ethanol and pentobarbital levels measured at 32 min after drug administration were not affected by Ro 15-4513. The selectivity of Ro 15-4513 and the mechanism(s) underlying its proconvulsant effect in reversing the actions of ethanol are discussed.