BACKGROUND/AIM: Colonoscopy is recommended to every patient with adenoma in rectosigmoid to disclose synchronous proximal neoplasms. The aim of this study was to determine whether characteristics of rectosigmoid adenomas are associated with proximal advanced neoplasms. PATIENTS/METHODS: One hundred consecutive symptomatic patients who underwent total colonoscopy and had rectosigmoid adenomas were included in the study. Patients with iron-deficiency anemia were excluded. All polyps were removed endoscopically. An adenoma was considered advanced if it had a diameter > 1 cm and/or villous and/or severe dysplasia histology were present. RESULTS: Advanced rectosigmoid adenomas were found in 55 of the 100 patients. Proximal neoplasms were found in 26 (26%) patients. In particular, nonadvanced adenomas were found in 15 (15%), advanced adenomas in eight (8%), and cancer in three (3%) patients. The presence of proximal neoplasms was related to neither sex, age, or presenting symptoms nor to any of the characteristics of rectosigmoid adenomas. On the contrary, the presence of advanced proximal neoplasms (advanced adenoma or cancer) was significantly correlated with the presence of advanced rectosigmoid adenomas, which were detected in 11 (20%) of the 55 patients with advanced and in none of the 45 patients with nonadvanced, rectosigmoid adenomas (odds ratio: 23.5, p = 0.001). Logistic regression analysis revealed that the presence of advanced rectosigmoid adenoma was the main predictor of advanced proximal neoplasms (beta: 1.34, p < 10(-6)). CONCLUSIONS: Among patients with rectosigmoid adenomas, 1) proximal advanced neoplasms appear to exist only in those with advanced adenomas and 2) baseline colonoscopy does not seem necessary in those without advanced adenomas.