BACKGROUND We undertook this study to establish the incidence of dumping syndrome after partial or total gastric resection and its association with patient's preoperative nutritional status as well as the clinical behavior with dietary management during a short-term follow-up period. METHODS This was a prospective study of consecutive patients >30 years of age and who were submitted to gastrectomy for gastric cancer or complicated ulceropeptic disease during a 48-month period in a highly specialized hospital. RESULTS A total of 42 patients were evaluated with a slight female predominance (n = 22, 52.4%). Twenty-nine cases (69%) had subtotal gastrectomy and 13 (31%) had a total gastrectomy. Patients had a medium age of 54.38 +/- 7.56 vs. 66 +/- 13.99 years, respectively (p = 0.034). Reconstruction techniques were Roux-en-Y gastrojejunostomy in 70% and Roux-en-Y esophagojejunostomy in 28.5%. We found dumping syndrome in 45% of the cases associated with acute or chronic undernutrition (p = 0.003). Fifty-three percent of the patients with dumping syndrome improved with adequate dietetic manipulation during a follow-up period of 211 days. CONCLUSIONS Although the majority of reconstructions were performed with dysfunctionalized small bowel segments, the incidence of dumping syndrome was 45%. Patient's preoperative nutritional status influenced the presence of clinical manifestations. Adequate dietary management reduced, in 53% of the patients, the presence of dumping symptoms during a short-term follow-up period.