To evaluate current practices regarding intensive-care units (ICU's), we collected data on 2693 consecutive admissions to a medical ICU during a two-year period and studied indications for admission, specific interventions, costs, and outcomes. The need for noninvasive monitoring rather than immediate major interventions prompted 77 per cent of the admissions. Only 10 per cent of monitored patients had subsequent indications for major interventions. The 23 per cent who required immediate interventions accounted for disproportionate shares of total charges (37 per cent) and deaths during hospitalization (58 per cent). Demographic and diagnostic data indicate that the aged and chronically ill have become the principal consumers of intensive care. Overall mortality during hospitalization was 10 per cent; cumulative mortality during follow-up study (mean duration, 15 months) was 25 per cent. We conclude that identification of sensitive predictors of complications and specific predictors of mortality can lead to more efficient and effective ICU practices.