Background: Lack of insurance coverage is one barrier limiting colorectal screening. In January of 1998, Medicare began reimbursing screening colonoscopies for beneficiaries with an increased risk for colorectal cancer. In July of 2001, coverage was expanded to all beneficiaries aged 50 years or older. Though previous studies have noted increased rates of colonoscopies following these policy changes, none have yet looked at their impact on the rates of first time procedures and the likelihood of polyp removal at the procedure. Methods: The study included a randomly selected cohort of cancer-free Medicare beneficiaries aged 65 years or older, and was limited to fee-for-service patients. Diagnosis and procedure codes for claims for colonoscopy and flexible sigmoidoscopy from January 1994 through December 2006 were used to categorize procedures by indication: screening, surveillance, or diagnostic. Procedures for a given patient were also classified as either their first under Medicare coverage if they had no previous procedure claims from date of Medicare enrollment or 1991, whichever was earlier, or as a follow up if they did. Results: The cohort consisted of 61,048 procedures from January 1994 through December 1997 (period I), 69,327 procedures from January 1998 through June 2001 (period II), and 141,101 procedures from July 2001 through December 2006 (period III). For each indication, the rates of colonoscopies increased following each change in reimbursement policy, whereas the rates of flexible sigmoidoscopies decreased. In addition, the percentage of colonoscopies that were first time procedures has increased significantly: 37.5% in period I to 43.8% in period II to 56.3% in period III (P < .0001). The rate of polyp removal at the procedure has also increased significantly: 23.1% to 27.6% to 33.3% (P < .0001). Conclusions: Our data shows expansion of Medicare coverage has been associated with increased colonoscopy use for every indication. Importantly this increase is greatest within the population of beneficiaries without a previous colonoscopy. The increased rate of polyp removal can be partially attributed to the higher yield of first time procedures and illustrates the efficacy of increased screening amongst those with no prior history of colonoscopy.