The Roux-en-Y gastric bypass (RYGB) is a demanding operation. It is more difficult to perform than most vertical pouch gastroplasties and is associated with a greater number of life-threatening complications. This study addresses the technical problems facing the bariatric surgeon when the RYGB is performed on patients weighing more than 500 lb. It represents an 8-year operative experience with 2050 morbidly obese patients, 23 (1.1%) of whom were classified as 'ultraobese'. Specific steps of the RYGB have been analysed and refined. Using the technical innovations described, the bariatric surgeon can perform the RYGB in the ultraobese patient with a reasonable degree of morbidity and mortality. Without the potential for safe surgical intervention, the prognosis for this group of patients is grim at best.