The records of 68 patients with hemoglobin SC disease and 68 age- and sex-matched control patients were reviewed for neurological problems. A significant increase in retinopathy, stupor/coma, and seizures was noted in the hemoglobin SC group. Hemiplegia, noted in two young patients, was probably also secondary to hemoglobin SC disease. Hemoglobin SC disease may often go unrecognized as a cause of stupor and coma in older patients without other obvious manifestations of a sickling hemoglobinopathy. Factors known to precipitate sickling crisis and the associated neurological complications should be avoided, especially in patients undergoing surgery or parturition.