We performed a retrospective utilization study covering a four-year period to determine how physicians familiar with colon transit scintigraphy (CTS) use it to manage patients with chronic constipation. Following CTS, there was a change is both frequency and likelihood of diagnosis. The diagnosis was changed in 51% of patients-37% of those considered to have slow transit constipation (STC) before CTS, 43% with obstructed defecation, and 64% with functional bowel disease (FBD). CTS increased the diagnostic likelihood in all groups. Of patients with the diagnosis of STC, 16% were considered "almost certain" before CTS while 83% were considered "almost certain" after CTS. For FBD comparable percentages were 13% and 62%. CTS may play a major role in the diagnostic work-up of patients with chronic constipation, both altering diagnosis and increasing diagnostic certainty.