Background: The optimal strategy for CRC post-treatment surveillance is unknown. The frequency and type of testing remains controversial, and it is unclear whether surveillance impacts rates of detection or survival. The purpose of this study was to determine if the intensity of post-treatment surveillance is associated with time to recurrence detection, treatment, or overall survival (OS). Methods: Primary records of a random sample of 10,636 Stage I-III CRC patients from Commission on Cancer accredited hospitals (2006-2007) were abstracted, and detailed results of surveillance testing were reviewed. Data was merged with records in the National Cancer Database (NCDB). A predicted and observed number of imaging and CEA tests per patient were determined and clustered by hospital to categorize patients into high (HI, O/E ≥ 1) or low intensity (LI, O/E < 1) categories. Results: 6,279 patients underwent imaging or CEA surveillance in the 3 years after CRC treatment. Patients with HI imaging (50.6%) or CEA (51.2%) had a mean of 2.9 imaging studies and 4.7 CEA tests. Patients with LI imaging underwent a mean of 1.4 imaging studies and 1.6 CEA tests. 5-year recurrence rates did not differ based on intensity of surveillance. Stage II and III patients who underwent HI imaging and CEA testing had a slightly higher resection rate, but this did not translate into an improvement in 5-year OS. Conclusions: High vs. low intensity surveillance was not associated with earlier detection of recurrent disease or improved OS. HI surveillance was associated with a slightly higher resection rate, but this did not result in a survival benefit. Our findings within a national hospital registry cohort failed to demonstrate a survival benefit of HI surveillance and suggest that an effective surveillance strategy may involve less frequent testing.