Continuous positive airway pressure (CPAP) applied through the nose completely prevented obstructive apnoea during all night testing in 50 patients with severe obstructive apnoea. In early 1981, we began a home treatment trial of nasal CPAP. Patients were treated in hospital for 3 to 5 nights, a period in which they were trained to fit the custom made nose-mask used to provide nasal CPAP. Patients subsequently continued treatment at home. Daytime somnolence resolved within days of starting therapy, and did not recur while the nasal CPAP unit was used on a regular basis. At present, we have 35 patients who have been on therapy for periods ranging between 3 and 30 months. Although each patient has displayed a reduction of severity of the underlying sleep apnoea when tested without nasal CPAP, the majority continue to require regular nightly nasal CPAP. In a few patients, treatment with nasal CPAP appeared to help in weight control such that obstructive apnoea and snoring have resolved. Nasal CPAP is a safe, fully effective therapy for obstructive apnoea, and can be used indefinitely by the patient at home.