BACKGROUND: Only limited data are available for assessing the medium and long-term outcomes after bariatric surgery. We report our own long-term results after biliopancreatic diversion with duodenal switch (BPD-DS). METHODS: The data from 51 patients with a theoretical >/=5-year follow-up were reviewed after BPD-DS performed from February 2002 to October 2004. The patients were assessed every 3 months during their first postoperative year, every 6 months during the second year, and annually thereafter. RESULTS: The preoperative body mass index (BMI) was 47 +/- 6.1 kg/m(2). The first 23 patients had undergone open BPD-DS. The same procedure was used (150-mL sleeve, 150-cm alimentary limb, and 100-cm common channel) for the 28 laparoscopic BPD-DS procedures, although 15 patients underwent conversion to laparotomy at the beginning of our experience. No patients died postoperatively. Of the 51 patients, 7 were not available for follow-up: 2 patients had died 9 months after BPD-DS (1 of myocardial infarction and 1 after ventral hernia repair), 1 underwent reversal, 1 refused follow-up after a complicated postoperative course, and contact was lost with 3 patients (7.8% lost to follow-up). The 5-year BMI was 31 +/- 4.5 kg/m(2), with a mean excess weight loss of 71.9% +/- 20.6%. Of the 44 patients, 7 (15.9%) had an excess weight loss of <50%; 4 of these unsatisfactory results occurred after revision BPD-DS. After primary BPD-DS, excess weight loss of 75.8% +/- 18.0% was observed. Biologic data were obtained for 85% of the patients at 5 years. The main vitamin and micronutrients parameters remained stable over time. However, a trend was seen toward an increase in the parathormone levels and difficulties in maintaining a normal vitamin D level despite updated vitamin supplementation. CONCLUSION: The results of our study have shown that BPD-DS achieves sustainable significant weight loss with >5 years of follow-up, with unsatisfactory results in <20% of cases. Although not statistically significant, revision surgery more often resulted in lesser weight loss, although this difference had almost vanished when the initial BMI was taken as a reference compared with the BMI before BPD-DS.