In 1994 and 1995, there were no specific CPT or HCPCS codes for screening FS, colonoscopy, or double-contrast barium enema. Because these tests may be used for either screening or diagnosis, we inferred that they were performed for screening using the following algorithm. We first identified these procedures from CPT codes (colonoscopy codes: 44388, 44389, 44392, 44393, 44394, 45378, 45380, 45383, 45384, and 45385; sigmoidoscopy codes: 45300, 45305, 45308, 45309, 45315, 45320, 45330, 45331, 45333, 45338, and 45339; and barium enema codes: 74270 and 74280). We then assumed that the procedures were performed as screening tests if there were no ICD-9 diagnosis codes of gastrointestinal tract symptoms, weight loss, or anemia (abdominal pain codes: 787.3, 789.0x, and 789.6x; altered bowel habits codes: 564.0 and 787.x; gastrointestinal bleeding code: 578.x; positive FOBT code: 792.1; weight loss code: 783.2; iron deficiency anemia code: 280.x; and anemia, unspecified, code: 285.9) associated with any physician visits within the previous 3 months. Because of this 3-month exclusion rule, we analyzed only claims submitted between April 1 and December 31 of each year so that we would have diagnosis data from the 3 months before a test was performed. Use of this screening algorithm may have underestimated the actual frequency of screening, as one of these diagnoses may have been given to justify performing the test, even if the true indication was screening. However, we have no way of accurately distinguishing the procedures coded in this way.