We prospectively studied all patients admitted to a multidisciplinary intensive care unit to determine how many of their diseases were iatrogenic and, of these, what number were potentially avoidable. Of 325 patients admitted in the course of one year, 41 (12.6%) were hospitalized because of iatrogenic disease. Many of these patients had concomitant serious illnesses. Nevertheless, 19 patients (46.3%) were admitted with iatrogenic disease resulting from therapeutic or technical errors that were potentially avoidable. latrogenic disease was fatal in eight cases, life-threatening in 13, moderate in 20.