Seventy-six patients with neurologic complications of cat-scratch disease are discussed. Encephalopathy occurred in 61, while 15 had either cranial or peripheral nerve involvement. The average age of the patients with encephalopathy was 10.6 years (range, 1 to 66 years), and almost twice as many males as females were affected in contrast to patients with uncomplicated cat-scratch disease, in which the ratio was almost equal. Fever was not documented in 50% of patients with encephalopathy and only 26% had temperatures higher than 39 degrees C. Convulsions occurred in 46% and combative behavior in 40%. Lethargy with or without coma was accompanied by variable neurologic signs. Results of laboratory studies, including imaging of the central nervous system, were inconsistent and nondiagnostic. Biopsy tissue from 14 patients showed histopathologic findings compatible with cat-scratch disease. The "English-Wear bacillus" was demonstrated by the Warthin-Starry stain in 10 of 14 skin or lymph node specimens. Of the 15 patients without encephalopathy, two children with facial nerve paresis displayed cranial nerve symptoms and/or signs, 10 patients had cat-scratch disease neuroretinitis, and three women had peripheral neuritis. All 76 patients recovered within 12 months; 78% recovered within 1 to 12 weeks. There were no neurologic sequelae. Treatment consisted of control of convulsions and supportive measures. Commonly used antibiotics administered to more than half of the patients were apparently ineffective.