We analyzed the outcome of 39 consecutive acute exacerbations of chronic obstructive pulmonary disease (COPD) in 35 patients requiring mechanical ventilation, in order to identify the features related to survival. Patients were divided into those surviving less (group A; n = 14) and more (group B; n = 24) than six months. Pulmonary function tests, arterial blood gas levels either on admission or while in a steady state, and nutritional parameters were similar in both groups. Only the duration of mechanical ventilation was longer in group A when compared to group B. In patients dying while being ventilated or surviving less than ten days after extubation, only the forced vital capacity (FVC) was different when compared to the rest of group A. The duration of mechanical ventilation was not related to age or the forced expiratory volume in one second (FEV1). Only a multivariate analysis accounting simultaneously for eight parameters could separate with 78 percent accuracy the different groups of patients; however, following this analysis, 23 percent of the patients in group B could have been falsely classified as nonsurvivors and perhaps rejected for mechanical ventilation. We conclude that the six-month survival of patients with COPD who required mechanical ventilation for an acute exacerbation of their disease cannot be predicted from simple data generally available to the physician in charge at the time of intubation.