Fifty-eight patients with AIDS disease were studied with MR imaging in the aim of detecting the grade of brain involvement. The examinations were performed with a 1.5 Tesla magnet. Thirty-seven showed white matter lesion (63.5%), twenty-five patients showed cerebral atrophy (43%), in eight patients the MR appearance was consistent with toxoplasmosis infection (13.5%), two patients showed a linfoma (3.4%) and two patients micrococcosis (3.4%). Seventeen out of the thirty-seven patients with white matter disease showed focal well circumscribed lesion (46%), while twenty showed diffuse involvement. Between the twenty-five patients with cerebral atrophy, twelve showed a prevalence of the cortical involvement and eight a subcortical atrophy. In five patients a concomitant, cortical and subcortical atrophy was found. Between the eight patients with neurotoxolesion and two of them a widespread encephalitis picture. The MR appearance of the two limphomas was that of periventricular, space occupying, masses. In two patients with micrococcis a nodular aspect of leptomeningeal lesions was found.