PURPOSE: The aim of this study was to retrospectively analyze a large group of CT and MRI examinations for appropriateness using evidence-based guidelines. METHODS: The authors reviewed medical records from 459 elective outpatient CT and MR examinations from primary care physicians. Evidence-based appropriateness criteria from a radiology benefit management company were used to determine if the examination would have met criteria for approval. Submitted clinical history at the time of interpretation and clinic notes and laboratory results preceding the date of the imaging study were examined to simulate a real-time consultation with the referring provider. The radiology reports and subsequent clinic visits were analyzed for outcomes. RESULTS: Of the 459 examinations reviewed, 284 (62%) were CT and 175 (38%) were MRI. Three hundred forty-one (74%) were considered appropriate, and 118 (26%) were not considered appropriate. Examples of inappropriate examinations included brain CT for chronic headache, lumbar spine MR for acute back pain, knee or shoulder MRI in patients with osteoarthritis, and CT for hematuria during a urinary tract infection. Fifty-eight percent of the appropriate studies had positive results and affected subsequent management, whereas only thirteen percent [corrected] of inappropriate studies had positive results and affected management. CONCLUSION: A high percentage of examinations not meeting appropriateness criteria and subsequently yielding negative results suggests a need for tools to help primary care physicians improve the quality of their imaging decision requests. In the current environment, which stresses cost containment and comparative effectiveness, traditional radiology benefit management tools are being challenged by clinical decision support, with an emphasis on provider education coupled with electronic order entry systems.