Intensive care is being scrutinized as a major factor in increasing health care costs. We examined 404 consecutive admissions to the medical ICUs at a university medical center to study patterns of consumption of ICU resources and the proportion of resources used by patients admitted for monitoring only. We found a skewed distribution of ICU resource consumption, with the "high-cost" 8 percent using as many ICU resources as the "low-cost" 92 percent. Forty-one percent of admissions did not receive acute ICU treatments, but these admissions consumed less than 10 percent of ICU resources. Reducing the number of patients admitted for monitoring will have a relatively small impact on hospital charges. Since over 70 percent of the high-cost patients died, improved understanding of prognosis and better physician-patient communication may substantially reduce the proportion of critical care resources expended on futile treatment.