Four hundred sixty-one consecutive admissions to the Pediatric Intensive Care Unit (PICU) were evaluated using the Therapeutic Intervention Scoring System (TISS). Patients requiring an increased level of care, defined as TISS points greater than or equal to 10, accounted for 75% of patient days in the ICU. Within this group, the primary reason for admission to the ICU was congenital heart disease, trauma, malignancy, respiratory failure, and sepsis. Survival was inversely related to TISS points, through TISS itself could not differentiate between survivors and nonsurvivors. The mortality rates for children who had a congenital malformation, a cardiac arrest before admission, or who developed acute failure secondary to other disease processes were significantly increased. Comparison of critically ill children and adults using TISS showed mortality rates that were similar. Assuming that the cost of intensive care is related to both seriousness of illness (assessed by TISS) and length of hospitalization, in this pediatric population the cost of hospitalization was not disproportionately high for nonsurvivors compared to survivors. Reduction in mortality rates in a PICU population will be dependent on factors largely uncontrollable buy ICU practitioners. This will come about by reduction in the numbers of congenital malformations and the prevention of childhood trauma.