In an attempt to identify clinical variables associated with unexpected death or unit readmission following discharge from a medical intensive care unit (MICU), 300 consecutive patients admitted to a MICU were prospectively identified and followed through their hospital stay. Of the 229 patients at risk, 37 (16 percent) experienced one or more unexpected unit readmissions (n = 30) or death (n = 7). In comparison to the patients without such complications (n = 192), these 37 patients differed with respect to age, diagnosis, and severity of illness on admission. In addition, these patients were sicker on initial unit discharge as manifested by higher heart and respiratory rates and lower hematocrit values. On multivariate analysis, age, acute physiology score on admission, and a diagnosis of upper gastrointestinal bleeding were independent predictors of unexpected outcome. It is concluded that patients at high risk for unit readmission or unexpected death are distinguished from other MICU survivors on several clinical parameters. Whether such information can be useful in individual discharge decisions is uncertain and requires further investigation.