Two patients with AIDS-related neurologic dysfunction were evaluated with both computed tomographic (CT) brain scans and magnetic resonance imaging (MRI). CT scans were essentially normal in both patients while MRI revealed focal lesions amenable to brain biopsy. Using newly developed instrumentation, MRI-guided stereotaxic brain biopsy was performed without complication. The benefits and impact of this new technology for the care of neurologically symptomatic AIDS patients is discussed.