OBJECTIVE: To assess patients' willingness to accept life-sustaining treatment when the expected outcome is a diminished mental health state. DESIGN: Structured interviews with a consecutive series of patients. SETTING: A university-based Department of Veterans Affairs Medical Center. PATIENTS: One hundred four male patients (mean age = 65.4 years; range 37-82) seen consecutively in a general medicine clinic. MEASUREMENTS: We assessed the acceptability of temporary ventilatory support of a hypothetical case of severe pneumonia. Patients were asked to consider mental health states involving minor cognitive deficits that varied only in their expected frequency and duration. RESULTS: All patients except one were willing to accept temporary life support in the management of severe pneumonia. Of these 103 patients, 76 patients specified the number of days they would allow themselves to be continued on intubation and ventilatory support. The length of time varied from 1 day to 2 years and was longer when patients reported having had a stroke of reported being in fair of poor health. Fifty patients were willing to accept all diminished mental health states, including the most severe state (F). Patients who reported having been in a medical intensive care unit were more likely to accept intubation in the most severe state (F). CONCLUSIONS: In the case of "severe pneumonia", about half of our older male veterans reported a willingness to accept intubation and ventilatory support even if it resulted in persistent cognitive disability. These results suggest that experience in a medical intensive care unit with the ventilators and experience with strokes may make patients more tolerant of treatments that may result in impaired cognitive function.