Alcohol causes significant sleep disturbance but the causes are not well understood. We investigated the relationship between alcohol use and periodic limb movements in a large population of patients at a sleep disorders center. The likelihood of having a clinically significant number of periodic leg movements (more than 20 per hour of sleep) was increased 3-fold in women who consumed two or more alcoholic drinks per day compared with those who did not (25% versus 8%). A similar relation was found among men (22% versus 13%). In addition, women who consumed two or more drinks per day were more likely to report symptoms of restless legs and to be diagnosed with restless legs syndrome. These findings suggest that periodic leg movements contribute to sleep disturbance in a significant proportion of alcohol users. Alcohol use may increase the frequency of periodic leg movements in susceptible individuals. On the other hand, subjects with symptoms related to periodic leg movements may be using alcohol to relieve symptoms, or the movements may be secondary to alcohol-induced sleep disturbance.