QUESTION OF THE STUDY: Some patients experiencing near-fatal asthma present with extreme hypercapnia (PaCO2 > or = 100 mm Hg), whereas others do not. The influence of this factor on short- and long-term outcome and quality of life in these patients is still unknown. PATIENTS AND METHODS: A series of 39 consecutive patients who had had an episode of near-fatal asthma between 1978 and 1992 were followed up. Long-term outcome and quality of life of the 12 patients who had experienced extreme hypercapnia were compared with those of the 27 patients who had not. RESULTS: Four patients died, but only 1 from asthma. Three patients were lost to follow-up. The remaining 32 patients had a median observation period of 12.7 years. The hypercapnic patients did not significantly differ from the others in past asthma history, subsequent hospitalizations, medication needs, pulmonary function tests, quality of life and impairment/disability. In the event of subsequent near-fatal asthma attacks, they tended to present with hypercapnia levels similar to those observed during the first episode. DISCUSSION: Extreme hypercapnia in near-fatal asthma tended to recur, but is not an aggravating long-term prognostic factor. Targeted surveillance of these high-risk patients should make it possible to reduce relapses and death rates from asthma.