To evaluate the long-term results of jejunoileal bypass in the treatment of morbidly obese adolescents, we studied 11 patients who underwent surgery between 1972 and 1974. More than 10 years after surgery, 45% of the patients had extremely satisfactory results (correction of morbid obesity). Three patients died within the year after surgery, two of them under extenuating clinical circumstances. There have been no subsequent deaths. All eight survivors were found to have metabolic abnormalities to various degrees. Two patients had a total of five pregnancies; each had one healthy infant, and three pregnancies ended in abortion (one spontaneous). Two patients had significant medical problems related to the procedure but basically remained in good health, whereas three patients had severe symptoms requiring reanastomosis. Of the five patients who continue with the bypass, none has become significantly obese. They have all maintained a weight loss of between 45 and 90 kg, and as adults express strong feelings in favor of the procedure. This series demonstrates that, although significant weight loss was maintained, and improvement in the quality of life for half of our patients was dramatic, side effects and complications continue to develop, mandating careful follow-up for an indefinite time.