A controlled study of growth in children receiving alternate-day versus daily corticosteroid regimens was performed with 60 children and adolescents with kidney grafts. The study started 14 to 27 months after transplantation in patients with normal graft function, after a graft biopsy. Thirty-five patients were available for the growth study; 17 were randomly allocated to receive alternate-day therapy and 18 remained on a daily regimen. The cumulative dose was similar in the two groups, as were bone age and renal function. After 1 year of follow-up, the mean statural growth, expressed as change in SD score, was significantly better in those on the alternate-day regimen (+0.49 +/- 0.42 SD/yr) than in those on the daily regimen (-0.12 +/- 0.53 SD/yr; p less than 0.005). The difference was also significant when prepubertal and pubertal children were analyzed separately. During the second year of the study most children who were receiving daily treatment were given alternate-day therapy; their mean growth velocity increased to +0.29 +/- 0.35 SD/yr (p less than 0.05 vs the first year); children who had been on the alternate-day regimen since the outset of the study continued to have similar positive SD scores (0.52 +/- 0.37 SD/yr). Renal function remained stable throughout the study regardless of corticosteroid regimen, except in the case of one patient undergoing daily therapy who had a rejection crisis. We conclude that in children with a kidney graft a given cumulative dose of corticosteroid has a significantly lesser inhibitory effect on growth velocity when given on alternate days.