In 106 consecutive biliopancreatic diversion patients, the small intestine was divided at its mid-point to create equal biliopancreatic and alimentary limbs, because several observations had suggested that this would lead to improved nutrition post-operatively. In order to test this hypothesis, the progress of these patients was compared with a similar group who had undergone a standard Scopinaro biliopancreatic diversion with a 250 cm alimentary limb. Four particular areas were studied--weight loss, hypoproteinemia, iron deficiency anemia and disturbance of bone metabolism. Patients with equal limbs lost 71% of their excess weight at 36 months, compared to 77% in the standard diversion. With the equal limbs the incidence of hypoproteinemia was reduced from 8% to 2% and the incidence of iron deficiency anemia decreased from 20% to 10%. The change had no effect on clinically symptomatic metabolic bone disturbance which occurred in 7% of the patients in both groups. In the authors opinion, these improvements justify continued division of the small intestine at its mid-point.