Compared two groups of Type I diabetic Ss, visually impaired and nonvisually impaired (N = 39), to a non-neurologic chronically ill group and a healthy group (N = 44) on the Halstead-Reitan Neuropsychological Test Battery and the Wechsler Adult Intelligence Scale. The diabetic groups performed like each other and worse than the other two groups on somatosensory examination, motor strength and motor speed tasks. Impairment was more consistent and pronounced among male diabetics than among female diabetics. The non-visually-impaired diabetic group performed worse than the other two groups on Trail Making Tests and Performance IQ. Diabetics performed like the chronic illness group and worse than the healthy group on Category Test. In diabetics, impaired neuropsychological performance tended to be associated with severity of disease and number of severe hypoglycemic episodes. Diabetics demonstrate neuropsychological impairment on tasks that require visual and motor efficiency, and somatosensory discrimination. Cognitive skills and memory remain intact among most diabetics despite greater risks among diabetics for electrolyte imbalance, neurotransmitter deficiencies, and coma.