We evaluated the effect of six-month treatment with growth hormone (GH) or low-dose oxandrolone in a group of boys with constitutional growth delay (CGD). Sixteen boys were randomly assigned to two treatment groups. Group 1 received GH (0.6 U/kg/week sc 5-6 times/week) and Group 2 received oxandrolone (0.07 mg/kg po). The boys of the two groups were closely matched for age (13.7 +/- 0.5 and 12.8 +/- 0.4 years) (mean +/- SE), chronologic age/bone age ratio (1.15 +/- 0.04 and 1.16 +/- 0.02), height standard deviation score (SDS; -2.7 +/- 0.4 and -2.5 +/- 0.3) and pretreatment height velocity (HV) (3.7 +/- 0.8 and 4.0 +/- 0.4 cm/year). Other known causes of short stature were excluded in all subjects, and none had taken long-term medication prior to the study. After 6 months of treatment HV increased to 7.5 +/- 0.4 and to 8.1 +/- 0.5 cm/year in group 1 and 2, respectively. Plasma IGF-I concentrations rose significantly after treatment in both groups. Predicted adult height was not significantly affected by either GH or oxandrolone treatment. We conclude that a short-term course of low-dose oxandrolone is as effective as GH to accelerate growth in boys with CGD. Low-dose oxandrolone represents an effective, cheap, and convenient therapeutic approach in boys with CGD.