Three intramuscular injections of 25 to 50 mg of testosterone hexahydrobenzoate were prescribed in 37 boys who presented with hypoplastic penis: 16 with micropenis and normally placed urethra, 21 with hypospadias. Ages ranged from 4 months to 9 years. In almost all children treated between the ages of 6 and 18 months, penis growth became normal for age. Growth and bone maturation were temporarily accelerated but in a parallel fashion, so that this very early androgen-therapy need not reduce the adult height of children thus treated.