An aversive therapy program was used to eliminate chronic ruminative vomiting in a nine‐month‐old infant, hospitalized with severe weight loss, malnutrition, and secondary medical complications judged potentially fatal by the pediatric staff. A trial of thickened feedings and continuous maternal attention conducted on the pediatric ward before this intervention proved ineffective. In contrast to previous uncontrolled case reports, the present study included an extended pretreatment baseline and a treatment reversal, in which potentially relevant variables such as ward routines, observers, and apparatus remained constant. During treatment, a series of 0.5‐sec shocks were delivered at 0.5‐sec intervals when a ruminating sequence was observed and then terminated when it ceased. Shock intensity was set at a level that resulted in a startle response and produced fussing but failed to elicit crying. Treatment location and the individuals present were systematically varied to facilitate generalization. Ruminating dropped from a five‐day baseline mean of 114 to a single instance on treatment Day 3. During the three‐day treatment reversal, in which the shock source was disconnected, ruminating increased from four instances on the first day to 10 by the third day. Because of clinical considerations, however, shock was re‐introduced before ruminating reached pretreatment baseline levels. Reductions in ruminating were accompanied by significant weight gains, a decrease in crying, and an increase in interactions with staff and parents. The infant was discharged on the tenth day of the second treatment period. Followup evaluations conducted nine months after discharge showed that, despite several instances in the immediate two‐week posttreatment period, rumination no longer occurred and developmental progress was within normal limits. This article presents detailed procedural descriptions, discusses the problem of determining when to terminate treatment, considers nutritional management, and compares the relative effectiveness of an alternative aversive stimulus, concentrated lemon juice.