Although previous studies have documented neuropsychological deficits in children with end-stage renal disease, few have evaluated and compared the cognitive functioning and the school performance of children with renal failure. The current study evaluated the influence of chronic renal failure on cognitive functioning and school performance in children and adolescents with end-stage renal disease undergoing dialysis and after renal transplantation. Participants were given standardized IQ and achievement tests to assess cognitive functioning and ability. Academic performance was determined by evaluating grades for the semester in which the testing was performed; a grade point average (GPA) was calculated based on a 4.0-point scale. The 11 dialysis patients and 13 transplant patients were comparable in age, race, sex, and socioeconomic status. Overall IQ and subtest scores demonstrated no differences between the two groups. Performance on the Woodcock-Johnson achievement tests showed that the transplant patients did better on achievement tests of written language (P = 0.04) and in school performance in English compared with dialysis patients (P < 0.05). Furthermore the dialysis patients tended to be below age and grade level in all areas, whereas the transplant patients were achieving at or above these levels. There were significant differences in the age equivalent scores between the dialysis and transplant patients in the areas of mathematics and written language (P < 0.05). However, when grades were evaluated there were no differences in overall GPA or in the mathematics GPA. Days absent were not different between the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)