PURPOSE: To determine the level of participation of nonradiologists in computed tomography (CT) and magnetic resonance (MR) imaging of the brain, head and neck, and spine at hospitals and at private offices and imaging centers in the United States. MATERIALS AND METHODS: The 1993 Part B Medicare Annual Database was used to determine the number of procedures performed by radiologists and nonradiologists at hospitals and at private offices or imaging centers. The fourth edition of the Physicians' Current Procedural Terminology was used to classify procedures. RESULTS: Of the 3,883,391 neurologic CT and MR imaging studies billed to Medicare in 1993, 3,148,088 (81%) were obtained in a hospital setting; only 58,005 (2%) of these studies were interpreted by nonradiologists. Of the 735,303 imaging studies (19%) obtained at a private office or imaging center, only 63,115 (9%) studies were interpreted by nonradiologists. Overall, nonradiologists performed only 121,120 (3%) of the neuroimaging examinations billed to Medicare nationwide in 1993. CONCLUSION: The level of participation of nonradiologists in the interpretation of results from neurologic CT and MR imaging billed to Medicare is minimal.