This study explores the patterns of recurrence after "curative" operation for colorectal cancer. For an 11-year period, 1960-1971, 281 evaluable patients were resected at the Peter Bent Brigham Hospital. Crude five-year survival in these patients was 49%, but only 10% of those with recurrence lived five years. A total of 69 patients relapsed during their lifetime and 34 additional patients were found to have metastases at death. The initial site of metastases were regional in 23 patients (33%) and distant in 32 (46%). Simultaneous regional and distant metastases were found in 13 (19%) for a total of 65% of patients having initial distant metastases. Approximate recurrence rates by site were: 30% for sigmoid and rectum, 20% for right colon, and 10% for transverse and left colon. Tumor size was a significant determinant of recurrence but did not select for regional or distant sites. Recurrence by Astler-Coller modification of the Dukes-Kirklin classification revealed 10% for A + B1, 33% for B2, 35% for C1, and 50% for C2. More than half of the patients with distant metastases (18/32) had solely hepatic metastases yet the total incidence of liver metastases as the initial site was only 8% of the total. In general, the site of the primary cancer was the most important determinant of the type of recurrence; the stage and site of the primary tumor were most predictive for eventual relapse.