Colorectal carcinoma in young patients reportedly has a poor prognosis. Several reviews have suggested multiple explantations, including a low index of suspicion, delay in diagnosis or uniquely virulent tumor cells. However, some recent articles have suggested that the outlook is not necessarily dismal. To identify any distinctive characteristics of colorectal cancer in young patients, we studied the difference of incidence, initial symptoms, duration of symptoms, the location, gross types and size of the tumor, depth of invasion, resectability, lymph node involvement, distant metastasis, tumor stage by Astler-Coller classification, histologic types and five-year survival rates between 91 cases of young patients (less than 35 years of age) with colorectal cancer and 915 cases of eldly patients (35 years of age or more) as control, who were operated at Yonsei University Medical College, Severance Hospital during the 18 year period between January 1971 and December 1988. The results obtained are as follows: 1) The incidence of colorectal carcinoma in the young among total colorectal cancer patients was 9.0% (91/1,006 cases). There were 44 males and 47 females in the young age group, and the male to female ratrio was 0.93 : l. 2) There were no differences in the clinical symptoms, location, size, gross types of tumor and resectability between the two groups. 3) The duration of symptoms was longer in the younger age group than in the older age group. 4) The incidence of lymph node involvement was significantly higher in the younger age group than in the older age group (62.8% vs 39.2%; p<0.001). 5) The incidence of modified Dukes C cases was significantly higher in the younger age group than in the older age group (49.5% vs 33.49% p<0.001). 6) The incidence of mucinous carcinoma was significantly higher in the younger age group than in the older age group (32.5% vs. 10.1%; p<0.001). 7) The cumulative five-year survival rate was significantly lower in the younger age group than in the older age group (34.1% vs. 58.0%; p<0.005). 8) Even in the same stage or in the same status of lymph node involvement or with the same histologic type, the five-year survival rate was significantly lower in the younger age group than in the older age group. We conclude that the colorectal caricr in younger patients is worse than older patients. This unfavorable prognosis in young patients with colorectal cancer may be related to delayed diagnosis, more malignant histologic feature and other unidentified causes such as host factor. We suggest that a high degee of index of suspicion and aggressive treatment is mandatory even in young patients.