OBJECTIVE--To estimate the cost of follow-up among colorectal cancer patients treated with curative intent based on the broad spectrum of surveillance strategies suggested in the literature. DESIGN--Economic analysis of the costs associated with 11 separate surveillance strategies. Charge data were obtained from the Part B Medicare Annual Data file and the Hospital Outpatient Bill file. SETTING--Ambulatory care. MAIN OUTCOME MEASURES--Medicare-allowed charges and an actual-charge proxy for 5 years of follow-up after treatment for colorectal cancer patients on a nationwide basis. RESULTS--Medicare-allowed charges varied widely for the 5 years of posttreatment follow-up from a low of $561 to a high of $16,492. When Medicare-allowed charges were converted to a proxy for actual charges using a conversion ratio of 1.62, the range was $910 to $26,717, a 28-fold difference in charges. CONCLUSIONS--Charges vary extensively across follow-up strategies, with no indication that higher-cost strategies increase survival or quality of life.