A bottom-up approach was used to determine the direct ICU cost on actual resource use (medication, laboratory tests, microbiological analysis, disposables, and clinical procedures) for patients with severe sepsis. To determine the total direct costs, center-specific personnel and basic bed ("hotel") costs were added to total resources consumed. Average hospital mortality of severely septic patients was 42.6%. Mean ICU length of stay (LOS) was 16.6 days. Survivors stayed on average 4 days longer than nonsurvivors. The mean direct ICU costs of care were 23,297+/-18,631 euros per patient and 1,318 euros per day. In comparison, average daily charges being paid for an ICU patient by the health care system in Germany are 851 euros (based on official statistics). Nonsurvivors were more expensive than survivors in total direct costs (25,446 vs. 21,984 euros) and in per day direct cost (1,649 vs. 1,162 euros). Medication makes up the largest part of the direct costs, followed by expenses for personnel. CONCLUSIONS. Patients with severe sepsis have a high ICU mortality rate and long ICU LOS and are substantially expensive to treat. Nonsurviving septic patients are more costly than survivors despite shorter ICU LOS. This is due to higher medication costs indicating increased efforts to keep patients alive.