This proposal is concerned with the study of the role of sleep posture in obstructive sleep apnea syndrome (OSAS). Major goals include: 1) establishing the importance of posture monitoring to reliable diagnosis and 2) demonstrating the utility of posture correction in the treatment of OSAS. Patients will be monitored for respiration and sleep posture in a sleep laboratory using standard techniques, and in their homes using portable equipment. Patients with a positional effect in their OSAS will wear a monitor/alarm device to prevent back sleeping while being monitored at home to assess improvement with posture correction. In Phase I, software and hardware methodology will be developed for home monitoring of respiration and sleep posture. Data will be collected for eventual use in support of a Premarket Approval application to the FDA. In Phase II, research will be performed at additional sites, utilizing the methodologies and experience obtained during Phase I, in order to provide sufficient data to ensure FDA approval. It is hoped that posture monitoring and sleep posture correction will become standard procedures in the diagnosis and treatment of sleep apnea, thus removing a current source of diagnostic error and obviating the application of potentially hazardous treatments where not necessary.