The effects of a 20-min play intervention by a child life teacher on two observed behaviors were investigated in Pediatric Intensive Care Unit (PICU) patients at the Johns Hopkins Hospital Children's Center. Eleven subjects, ranging in age from 2--13 years, were observed using a Preintervention--Intervention--Postintervention design with a 3-min time sampling technique to measure the change occurring when structured play activities were introduced into the PICU environment. Significant positive changes were noted between Preintervention and Intervention in (1) affect and (2) interaction with materials. In the Postintervention period, these behaviors fell close to Preintervention levels, suggesting that the positive changes were not maintained in the absence of the Intervention condition. The results indicate that while play intervention in the PICU environment can have beneficial effects on patient's behavior, the effects of such intervention are short-lived. These data hold important implications for the staffing requirements needed to provide opportunities for the positive behavior changes to occur.