Objective To define infection rates in patients with Pediatric Risk of Mortality (PRISM) scores > and 72 hr. Methods The baseline state of the patients on admission was determined by a designated intensivist using the PRISM score. Other variables included age, length of stay, and hospital day of onset of infection. Infections were identified by a designated intensivist who undertook prospective daily bedside observation, chart, radiographic, and laboratory review. Measurements and Main Results Equal portions of patients had PRISM scores < and >10. Significantly more infections occurred in the high PRISM population (10.8% vs. 3.4%, p < .001). This association held through age, service, and length of stay. Sensitivity, specificity, positive and negative predictive values of a PRISM score >10 were 75%, 53%, 11%, and 97%, respectively. Bacteremias accounted for 36% of infections, skin/eye/drain site 22%, respiratory 16%, wound 15%, and urine 9%. The most prevalent organisms were coagulase-negative staphylococci (32%), Pseudomonas aeruginosa (23%), Candida sp. (20%), and S. aureus (9%). Conclusions A PRISM score >10 on PICU admission characterizes a population within the PICU at increased risk of infection. However, 93% of patients did not develop infection and thus, a negative predictive value of 97% yields little additional information. (Crit Care Med 1991; 19:160)