Fifty-one children 6-17 years of age rated the severity of nausea, vomiting, and the extent to which chemotherapy bothered them during each course of chemotherapy. Sixteen patients had no symptoms and the doses administered to 16 others were not constant so that matched courses could not be assessed. After baseline measurement of two matched courses, the remaining 19 patients were randomized to receive hypnosis or supportive counseling during two more matched courses. An additional course with no intervention was assessed in half of the patients. No significant reduction of symptoms was demonstrated prior to intervention. However, intervention with both hypnosis and supportive counseling was associated with significant reductions in nausea, vomiting, and the extent to which these symptoms bothered patients (all p less than 0.001). Also, after termination of intervention, symptom ratings remained significantly lower than baseline. The data indicate that chemotherapy-related nausea and emesis in children can be reduced with behavioral intervention and that reductions are maintained after intervention has been discontinued.