The purpose of a single-subject randomized trial is to assess objectively the efficacy of a specific therapeutic intervention in an individual patient. Treatment is randomly alternated with placebo over a number of study periods. Specific outcome measures are recorded blindly and later compared via paired statistical analysis. Single-subject trials have long been successfully performed in adults, but rarely in children. We present single-subject trials of two pediatric patients done to assess the effect of cisapride on symptoms arising from gastroesophageal reflux. In the first patient, the drug affected neither vomiting nor gagging, although stool frequency increased. Since the symptoms of concern were unaffected, cisapride was discontinued. In the second patient, use of cisapride led to a significant decrease in vomiting and wheezing; the drug was therefore incorporated into the therapeutic regimen. Single-subject randomized trials are inexpensive and simple and can be used by the family physician, pediatrician, or pediatric surgeon in daily practice. They permit the rational use of effective therapy and the abandonment of ineffective measures.