Sleep disturbances of alcoholics while actively drinking and at the beginning of, and during, abstinence were frequently reported. Recently, Gillin et al. (1994) showed that a high "REM sleep pressure" at the time of admission to a 1-month inpatient alcohol treatment program predicted the relapse in nondepressed patients with primary alcoholism at 3 months following hospital discharge. We investigated 24 patients with primary alcoholism after 2-3 weeks abstinence in the sleep laboratory; in 15 of these patients the cholinergic REM sleep induction test (CRIT) with 10 mg galanthamine was performed additionally. In comparison with an age- and sex-matched healthy control group, patients had a heightened "REM sleep pressure" including shortened REM latency and increased REM density. A decrease of serotonergic neurotransmission is proposed as being the neurochemical mechanism to explain the results in alcoholic subjects. Follow-up investigations will clarify whether the sleep abnormalities in alcoholism are state- or trait-markers and whether they are suitable to predict the relapse risk.