PURPOSE: Prognostic factors for patients who underwent colorectal cancer surgery, are such as clinical staging, possibility for curative surgery, and pathologic findings. But the age as a prognostic factor is still controversial. Therefore, we investigated the significance of age factor in colorectal cancer between young and older patients. METHODS: The study subjects included 755 patients who underwent surgery for colorectal adenocarcinoma from January 1, 1990 to March 31, 1999 in Kangnam St. Mary's Hospital, Seoul, Korea. Average follow-up period was 24.8 24.4 months. The patients were divided into younger than 40 and older than 74 year-old groups and compared with control group including the age from 40 to 74. The prognosis of each group was evaluated according to the sex, staging, characteristics of tumor, family history, recurrence rate and patterns, pathologic findings, possibility for curative surgery, and survival rate. RESULTS: Younger than 40 year-old group included 65 patients (8.6%) and older than 74 year-old group included 77 patients (10.2%). Their control groups included 613 patients (81.2%). There were no significant differences in tumor location, sex ratio, stage distribution, recurrence rate and patterns between the study and the control groups. However, there was significant higher incidence of family history in younger than 40 year-old group (7.7% vs 0.3%, P<0.05). Although there was no statistical significance, it is noteworthy that the ratio of undifferentiated or mucinous type were higher in younger than 40 year-old group than control group. Comparing the survival rates for each stage, the advanced stage of older than 74 year-old group had lower survival rate than control group (P<0.05). CONCLUSIONS: Low survival rate in the older group can be explained by poor general condition and the high ratio of palliative surgery. The prognosis of cancer in the young age can not be poor just because it is discovered at the young age itself and it can be improved by careful follow-up in patients with familial history and early diagnosis and radical surgery in patients without familial history. However, it must be noted that younger patients have higher risk for undifferentiated or mucinous type.