The effects of alpha-methyl-Dopa at several dose levels on waking-sleep cycle of 175 mice from two inbred strains (C57BR and C57BL/6) have been studied. The results showed that each dose (25, 50, 100, 200 and 400 mg/kg), of alpha-methyl-Dopa completely suppresses paradoxical sleep (PS), after a period of sedation. Duration of PS inhibition varied as a function of dose, time of injection, and strain of mice. Using a multiple injection schedule of one injection per day for 5 consecutive days, there was suppression of nocturnal PS followed at the 4th day by rebound during day light hours.