Background and Study Aims: Food residue is often seen in the gastric remnant after partial gastrectomy, making it difficult to diagnose early cancer in the residual stomach. The aims of this study were to clarify the risk factors for the accumulation of food residue, and to study methods of preparation for endoscopy in patients who had undergone distal gastrectomy. Patients and Methods: 374 endoscopic examinations of patients who had undergone distal gastrectomy for gastric cancer were compared with 2168 endoscopic examinations in patients without a history of gastrectomy. Relationships between the presence of food residue and a number of clinical factors, including patient preparation, were evaluated by univariate and multivariate analyses. Results: Food residue in the gastric remnant was observed in 70 examinations (18.7 %), a significantly higher proportion than that found in control patients (0.3 %). From multivariate analysis, underlying diseases (endocrine, metabolic, or connective tissue disease), Billroth type I reconstruction, and postoperative gastric retention were found to be independent risk factors for the accumulation of food residue. Diet preparation (a liquid diet plus aclatonium napadisilate) significantly decreased the incidence of food residue. Conclusions: Our diet preparation method can be recommended as a preparation for upper gastrointestinal endoscopy in patients who have undergone distal gastrectomy, especially in patients with additional risk factors.