Background: In the literature, suggested strategies for the follow-up of colon cancer patients after potentially curative resections vary widely, The optimal regimen to monitor for recurrences and new primary tumors remains unknown. The nationwide cost impact of wide practice variation is also unknown. Methods: The 1,070 members of The Society of Surgical Oncology (SSO) were surveyed using a detailed questionnaire to measure the practice patterns of surgical experts nationwide. Respondents were asked how often they use nine separate methodologies in followup during years 1-5 postsurgery for TNM stage I, II, and III patients. Costs were estimated for representative less and more intensive strategies. Results: Evaluable responses were received from 349 members (33%). Office visit and carcinoembryonic antigen analysis were performed most frequently. SSO members generally see patients every 3 months in years 1-2, every 6 months in years 3-4, and annually thereafter. There was wide variability in test ordering patterns and moderate variation between SSO and previously surveyed American Society of Colon and Rectal Surgeons members. The charge differential between representative less and more intensive follow-up strategies for each annual U.S. patient cohort is similar to$800 million. Conclusions: Actual practice patterns vary widely, indicating lack of consensus regarding optimal follow-up. The enormous cost differential associated with such variation is difficult to justify because there is no proven benefit of more intensive follow-up.