Oxygen saturation was measured in 37 patients with sleep-related breathing disorders over 2 nights: after alcohol intake and under control conditions. Both the number of 3% oxygen desaturation per hour (ODI3) and the lowest saturation (LSAT) were significantly aggravated after alcohol ingestion. Oxygen saturation was degraded in 28 cases after alcohol intake. In 69% of the cases in which ODI3 increased after alcohol ingestion, the aggravation during the alcohol metabolism time was noted. No correlation was found between the quantity of alcohol and oxygen desaturation following alcohol ingestion. Our study revealed that alcohol aggravates sleep-related breathing disorders.