OBJECTIVE: To assess the effect of nutritional supplementation on growth and puberty in constitutionally delayed children. PATIENTS: One hundred and two boys, 13.6-15.5 years of age, who were referred because of short stature and delayed puberty. METHODS: The boys were randomly allocated to one of the following treatment groups: oxandrolone therapy, 5 mg/day for 6 months (n = 15), testosterone depot, 100 mg monthly for 3 months (n = 15) or for 6 months (n = 20), nutritional programme (n = 17), oxandrolone and nutritional programme (n = 15) or passive observation (n = 20). Boys in the nutritional programmes received 12 mg/day iron and 6000 IU/week of vitamin A. Outcome measurements were of height, weight, pubertal signs, dietary intake, serum vitamin A, iron, GH and IGF-1. RESULTS: Six months of vitamin A supplementation induced growth acceleration similar to that seen in the oxandrolone- and testosterone-treated children, and significantly greater than in the observation group (9.3 ± 2.9 vs. 4.0 ± 0.9 crn/yr, P < 0.001). Whereas in the vitamin A-supplemented group, puberty (increase in testicular volume ≥ 12 ml) was induced within 12 months. In all testosterone-treated patients, pubic hair was noted within 3 months and a testicular volume of ≥ 12 ml was observed 9-12 months after the initiation of therapy. No pubertal signs were noted in the observation group during this time. CONCLUSIONS: Subnormal vitamin A intake is one of the aetiological factors in delayed pubertal maturation. Supplementation of both vitamin A and iron to normal constitutionally delayed children with subnormal vitamin A intake is as efficacious as hormonal therapy in the induction of growth and puberty.