Long-sleep (LS) and short-sleep (SS) mice were pretreated with either propranolol or phentolamine, followed by a hypnotic dose of ethanol. Pretreatment with propranolol, but not phentolamine, significantly reduced ethanol sleep time in LS mice. The SS mice were not affected. In a second study propranolol pretreatment was given subsequent to ethanol at various doses, different for each line, that produced similar sleep time durations in both lines. Under these conditions, propranolol decreased sleep time in both LS and SS mice. These data lend support to the idea that noradrenergic mechanisms play a role in the mediation of the hypnotic effects of ethanol.