Background: In the non-superobese population, consensus is currently unavailable in bariatric surgery. We report the results of a prospective comparison of vertical banded gastroplasty (VBG) and Roux-en-Y gastric bypass (RYGBP) in a non-superobese population. Methods: From 1994 to 2000,179 patients with clinically severe obesity underwent various surgical procedures. in our department. During this time a prospective study was undertaken in order to compare VBG with RYGBP in morbidly obese patients with a BMI < 50 kg/m(2). Based on specific criteria including eating behavior, 68 patients were selected to undergo RYGBP and 35 VBG. All patients have undergone complete follow-up evaluation at 1, 3, 6, and 12 months postoperatively and every year thereafter. Results: All patients have now completed their 5th postoperative year. Mean follow-up period to date is 96.5 +/- 12.2 months for VBG and 67.6 +/- 11.3 months for RYGBP. 3 patients (8.6%) in the VBG group and 9 patients (13.2%) in the RYGBP group are lost to follow-up. Mean excess weight loss (EWL) was always better in the RYGBP group (P=0.0013). The percentage of failure, defined as EWL < 25%, was not significantly different between the two procedures. No statistically significant differences were observed between the 2 groups in the total number of non-metabolic complications, and the only statistically significant difference observed in metabolic complications was vitamin B-12 deficiency after RYGBP. Frequency of vomiting was significantly less and quality of eating significantly better in RYGBP than in VBG patients. Conclusion: This prospective long-term study, with nearly complete follow-up, suggests that in the nonsuperobese population, preoperative eating habits may play a role in choosing the most appropriate bariatric operation for each patient. Although RYGBP is associated with better mean weight loss outcomes, the percentage of patients who achieved and maintained >= 50% EWL after VBG in this pre-selected patient population was not significantly different. Each type of operation has advantages and disadvantages, and, if properly chosen, a purely restrictive procedure can be successful for some patients. Therefore, it can be said that the decision regarding which bariatric procedure to perform in non-superobese patients must be based on in-depth preoperative evaluation as well as the patients' own preferences and outcome expectations.