In order to evaluate the effectiveness of follow-up in detecting potentially curable recurrences after radical surgery for colorectal cancer, we compared the results in 368 patients undergoing regular follow-up with those in 139 patients outside the follow-up program. The cancer-related 5-year survival rate was 72% in the follow-up group and 62% in the non-follow-up group (difference not significant). Cancer recurrences were more common in the follow-up group than in the group that was not followed (32% versus 21%; p less than 0.02). Curative reoperations were performed in 21% and 7%, respectively (p less than 0.01) of patients with recurrent cancer in these two groups. The cancer-related 5-year survival rate after curative reoperations was 47%. Despite these differences, only the initial Dukes' classification had an independent influence on the survival rate. It is concluded that regular follow-up detects more recurrent cancers, enabling radical reoperations significantly more often than when there is no follow-up. The outcome after curative reoperations is encouraging. These aspects favor regular follow-up of patients with colorectal carcinoma after curative operations.