All patients (n = 1308) admitted to a multidisciplinary intensive care unit (ICU) during a 5-year period (1979-83) were followed prospectively. The in-unit mortality was 18% and the in-hospital mortality (mortality during ICU-stay plus mortality during the ensuing hospital stay) was 29%. Increasing age was associated with increasing in-hospital mortality, up to 40% mortality rate in patients aged 80 years and older. Using multiple logistic regression analyses, prognostic factors for mortality were identified. Risk factors for death in the ICU included age, cardiovascular diseases, sepsis, adult respiratory distress syndrome and acute renal failure. Cancer did not appear as a risk factor. The mortality during the ensuing hospital stay, however, was significantly influenced by cancer as well as the aforementioned risk factors. When controlled for severity of illness, expressed by the level of organ system failure after 48 h of ICU treatment, only sex, sepsis and severity of illness showed significant influence on the mortality in the ICU, and only sex and severity of illness significantly influenced mortality during the ensuing hospital stay after discharge from the ICU.