• We evaluated posttransplantation growth, bone maturation, and adult height in 20 adolescents who had received kidney transplants at the age of 10.5 to 17 years. Nine patients (five male, four female) were treated with cyclosporine and low-dose prednisolone, and 11 children (six male, five female) were treated with azathioprine and high-dose prednisolone. The cumulative dose of steroids after transplantation was significantly lower in the cyclosporine-treated group. Bone age, according to the radius-ulna-short bones method of Tanner and Whitehouse, was almost the same in both groups at the time of transplantation (15.0 and 14.6 years for male subjects, 13.3 and 13.1 years for female subjects). Predicted adult height (Tanner-Whitehouse Mark II-method of Tanner et al) and target height were estimated at transplantation. Adult height was defined as achieved when bone age in male subjects had reached 18 years and, in female subjects, 16 years. Bone maturation of the cyclosporine-treated patients occurred at a normal rate (0.92 bone-age years per chronologic year), whereas the azathioprine-treated group exhibited a significantly slower rate (0.56 bone-age years per chronologic year). The growth rate per year for the cyclosporine-treated group was more than double that of the azathioprine-treated group (3.0 cm vs 1.4 cm). The adult height of the cyclosporine-treated group exceeded the predicted adult height by a mean of 1.3 cm, but the azathioprine-treated group missed it by 3.9 cm. Target heights could not be achieved in any group. Kidney function was significantly lower in the cyclosporine- vs the azathioprine-treated group, but no patients suffered from severe renal insufficiency. We conclude that cyclosporine and low-dose prednisolone are associated with normal bone maturation and a better prognosis for final height in children with renal transplants.