During puberty growth velocity increases within 3 years from a prepubertal nadir to a maximum, in male to 9-10 cm/year, in female to 7-9 cm/year. This spurt is triggered by the androgenic steroids, in male mainly by testicular testosterone. In patients with anorchia the pubertal growth spurt is missing. The androgens have a dual effect. 1. As comes forth from observations in hypopituitary dwarfs being treated with constant replacement doses of hGH, these steroids potentiate the growth-stimulatory effect of hGH. In order to continue growing at all, these dwarfs need the additional medication of androgenic or anabolic steroids if they are hypogonadotrophic. 2. As demonstrated by our measurements of the nocturnal hGH secretion, androgenic steroids enhance the spontaneous production of hGH by a factor of 2-3. Biologically active androgens appear to be a conditio sine qua non for longitudinal growth after age 11-12. This is in concordance with the statement that adult male castrates are no giants as has often been claimed. The rather tall eunuchs in Istanbul were no Turks but as a rule Sudanese negroes who are racially much taller than Turks.