Fifty patients with chronic obstructive pulmonary disease (COPD) who survived their first artificial ventilation were followed for 15 years. Five-year survival was 30%, median survival 23.5 months, and average survival 44.9 months. Sudden death occurred in 47% of the patients (40% at home and 7% in the hospital). Using multivariate analysis, survival correlated positively and significantly with partial pressure of arterial oxygen (PaO2) on discharge (P less than 0.02), presence of wheezes or rhonchi (P less than 0.02), absence of right heart failure on admission (P less than 0.02), and male sex (P less than 0.05), and negatively with age (P less than 0.03). Sixty percent of the patients were artificially ventilated at least twice. Prognosis was better as the number of ventilations increased after the first ventilation. Our finding that discharge PaO2 was the factor that correlated best with survival suggests that treatment for these patients consist of continuous long-term use of domiciliary oxygen.