To calculate overall pediatric intensive care unit (PICU) efficiency rates, 1668 patients representing 6962 patient-days were studied in eight PICUs. The contributions to inefficiency by two patient groups--low-risk monitored patients and potential early-discharge patients--were quantified using measures of daily mortality risk and therapeutic assessments. Low-risk monitored patients never received a unique PICU therapy and had daily mortality risks less than 1%. Potential early-discharge patients were similar to the low-risk monitored patients except that their unnecessary PICU use came only on their last consecutive day(s) of PICU stay. Efficiency ratings ranged from 0.894 to 0.547 in the eight PICUs. Low-risk monitored patients constituted from 16% to 58% of the PICU patient populations and used from 5.4% to 34.5% of the total days of care. Potential early-discharge patients constituted from 12% to 29% of the populations and the potential early-discharge days of care ranged from 5.1% to 17.2% of the total days of care. These results indicate that large disparity exists in efficiency among PICUs. Efficiency rates of greater than 0.80 seem to be a reasonable goal.