Insomnia and alcoholism are significantly associated in community surveys and patient samples. Insomnia occurs in 36–72% of alcoholic patients and may last for weeks to months after initiating abstinence from alcohol. Some correlates of insomnia in alcoholic patients are identical to those observed in non-alcoholic insomniacs, including anxiety and depression, tobacco smoking, and the use of alcohol to aid sleep. Other studies suggest that as the severity of alcoholism increases, so does the likelihood of insomnia in alcoholic patients. In the sleep laboratory, alcoholic patients who complain of insomnia have disrupted sleep continuity when compared to alcoholic patients without insomnia complaints. Recently sober alcoholics are also more likely than non-alcoholics to have sleep-disordered breathing and increased periodic leg movements, which might contribute to insomnia in some alcoholic patients. The co-occurrence of insomnia and alcoholism is clinically significant because alcoholism can exacerbate the adverse consequences of insomnia (e.g. mood changes and performance decrements) and because insomnia among patients entering treatment for alcoholism has been significantly associated with subsequent alcoholic relapse. Baseline polysomnographic correlates of subsequent relapse include prolonged sleep latency, decreased sleep efficiency and total sleep time, increased rapid eye movement sleep pressure, and decreased slow wave sleep. Whether treatment of insomnia in alcoholic patients reduces relapse rates is unknown, but preliminary treatment guidelines that accommodate the special characteristics of alcoholic patients are provided, with a goal to reduce daytime impairment and psychological distress.