Jejunoileal bypass for morbid obesity was performed on 182 patients between 1971 and 1982. At 19 years' follow-up 60 (33 per cent) have had to undergo reversal. The compelling reasons for reversal were life-threatening malnutrition, immune complex disease, renal oxalate stones, osteomalacia and severe electrolyte disturbance. All patients gained weight after reversal of the jejunoileal bypass; most gained all the weight they had lost. Thirty-one patients returned to grade III obesity and 14 to grade II. Twelve patients had an associated vertical gastroplasty: ten regained their previous weight and only two stayed within normal weight. Patients were generally free from bypass-associated symptoms and complications apart from arthralgia and arthritis. This report concludes a series of articles published by the authors on jejunoileal bypass over the past 20 years describing the rise and fall of this surgical procedure.