In order to describe the outcomes of patients hospitalized with an acute exacerbation of severe chronic obstructive pulmonary disease (COPD) and determine the relationship between patient characteristics and length of survival, we studied a prospective cohort of 1,016 adult patients from five hospitals who were admitted with an exacerbation of COPD and a PaCO2 of 50 mm Hg or more. Patient characteristics and acute physiology were determined. Outcomes were evaluated over a 6 mo period. Although only 11% of the patients died during the index hospital stay, the 60-d, 180-d, 1-yr, and 2-yr mortality was high (20%, 33%, 43%, and 49%, respectively). The median cost of the index hospital stay was $7,100 ($4,100 to $16,000; interquartile range). The median length of the index hospital stay was 9 d (5 to 15 d). After discharge, 446 patients were readmitted 754 times in the next 6 mo. At 6 mo, only 26% of the cohort were both alive and able to report a good, very good, or excellent quality of life. Survival time was independently related to severity of illness, body mass index (BMI), age, prior functional status, PaO2/FI(O2), congestive heart failure, serum albumin, and the presence of cor pulmonale. Patients and caregivers should be aware of the likelihood of poor outcomes following hospitalization for exacerbation of COPD associated with hypercarbia.