OBJECTIVE:The demand for intensive care beds far exceeds their availability in many European countries. Consequently, many critically ill patients occupy hospital beds outside intensive care units, throughout the hospital. The outcome of patients who fit intensive care unit admission criteria but are hospitalized in regular wards needs to be assessed for policy implications. The object was to screen entire hospital patient populations for critically ill patients and compare their 30-day survival in and out of the intensive care unit. DESIGN:Screening teams visited every hospital ward on four selected days in five acute care Israeli hospitals. The teams listed all patients fitting a priori developed study criteria. One-month data for each patient were abstracted from the medical records. SETTING:Five acute care Israeli hospitals. PATIENTS:All patients fitting a priori developed study criteria. INTERVENTIONS:None. MEASUREMENTS AND MAIN RESULTS:Survival in and out of the intensive care unit was compared for screened patients from the day a patient first met study criteria. Cox multivariate models were constructed to adjust survival comparisons for various confounding factors. The effect of intensive care unit vs. other departments was estimated separately for the first 3 days after deterioration and for the remaining follow-up time. Results showed that 5.5% of adult hospitalized patients were critically ill (736 of 13,415). Of these, 27% were admitted to intensive care units, 24% to specialized care units, and 49% to regular departments. Admission to an intensive care unit was associated with better survival during the first 3 days of deterioration, after we adjusted for age and severity of illness (p =.018). There was no additional survival advantage for intensive care unit patients (p =.9) during the remaining follow-up time. CONCLUSIONS:The early survival advantage in the intensive care unit suggests a window of critical opportunity for these patients. Under economic constraints and dearth of intensive care unit beds, increasing the turnover of patients in the intensive care unit, thus exposing more needy patients to the early benefit of treatment in the intensive care unit, may be advantageous.