A histopathologic analysis of the 294 polyps in a proctocolectomy specimen from a 21-year-old male patient was performed. Evaluating the locations, sizes, growth patterns and neoplastic changes of the polyps, the following results were obtained. 1) Of the total 294 polyps, 79(26.9%) were hyperplastic ones and 215(73.1%) were juvenile ones. The juvenile polyps were mixed focally with hyperplastic component, adenomatous component, or villous component. The polyps mixed with neoplastic components(adenomatous or villous component) were 28 of 215 juvenile polyps. 2) The most of polyps(206;70.1%) were crowded in the rectosigmoid region, but a considerable number of polyps(44;15.0%) were identified in the cecum. Others were scattered in the ascending colon(25;8.5%), descending colon(12;4.1), and the transverse colon(7;2.4%). 3) The average size of the juvenile polyps was larger than that of hyperplastic ones. The neoplastic changes in the juvenile polyps were seen more frequently in the larger polyps and in the pedunculated and multilobulated ones. 4) In consideration of the neoplastic changes, the juvenile polyps were regarded as preneoplastic lesions which could evolve adenomatous or villous polyps.