Intellectual and reading skills were evaluated and related to disease variables in 42 children with Type I (insulin-dependent) diabetes. A significant interaction revealed lower Wechsler Intelligence Scale for Children-Revised (WISC-R) Performance IQ for children with early disease onset (less than 7 years) and long disease duration (greater than or equal to 5 years). IQ scores were nevertheless in the average range. Although there was no specific pattern of visual spatial impairment, functioning on the Performance subtests was uniformly lower for this group. Slower responding to the timed tasks of the Performance scale may account for generally lower scores. Children with early onset-long duration also evidenced higher rates of reading and memory impairment. These results indicate the importance of ascertaining educational skills in diabetic children before planning diabetic treatment regimens, especially for children with disease of early onset and long duration, who may be especially vulnerable to skill deficits.