One of the most frequent questions asked of a pediatric anesthesiologist is "What are the risks of anesthesia for my child?" Unfortunately, few studies have examined the consequences of general anesthesia in children. We used data from a large pediatric anesthesia follow-up program at Winnipeg Children's Hospital (1982-1987) to determine rates of perioperative adverse events among children of different ages. A check-off form was completed by a pediatric anesthesiologist for each case (n = 29,220) and a designated follow-up reviewer examined all anesthesia forms and hospital charts to ascertain adverse effects for children less than 1 mo, 1-12 mo, 1-5 yr, 6-10 yr, and 11-16 yr of age in the intraoperative, recovery room, and postoperative periods. The majority of the children were healthy, and 70% had no preoperative medical conditions. Infants less than 1 mo old were more likely to be undergoing major cardiac or vascular procedures, whereas the older children had mainly orthopedic or otolaryngologic procedures. Infants less than 1 mo old had the highest rate of adverse events both intraoperatively and in the recovery room. The main problem in this age group was related to the respiratory and cardiovascular systems. In children over 5 yr of age, postoperative nausea and vomiting was very frequent, with about one-third of the children experiencing this problem. When all events were considered (both major and minor), there was a risk of an adverse event in 35% of the pediatric cases. This contrasts with 17% for adults. This morbidity survey helps to focus on areas of intervention and for further study.