Table 2.

Tanner stages for genital development and pubic hair growth in boys^a.

Tanner stage	Genital development		Pubic hair growth
	Definition	Age range	Definition	Age range
1	Prepubertal stage; testes, scrotum and penis are of about the same size and proportion as in early childhood.		Prepubertal stage; no pubic hair, the fine hair is not further developed than that over the abdomen.
2	The scrotum and testes have enlarged and there is a change in the texture and reddening of the scrotal skin.	9.5–13.8	Sparse growth of long, slightly pigmented, downy hair, straight or slightly curled, appearing mostly at the base of the penis.	11.3–15.6
3	Growth of the penis has occurred, at first mainly in length but with some increase in breadth. There has been further growth of testes and scrotum.	10.8–14.9	Considerably darker, coarser and more curled hair starts to spread sparsely over the pubic area.	11.8–16.0
4	Penis further enlarged in length and breadth with development of glans (wider area at the end of penis). Testes and scrotum further enlarged. There is also further darkening of the scrotal skin.	11.7–15.8	Hair is now more likely in adult type, but the area covered by the hair is still considerably smaller than in most adults. There is no spread to the inner thighs.	12.2–16.5
5	Penis and scrotum are now in adult size and shape. No further enlargement takes place after stage 5 is reached.	12.7–17.1	The quantity and type of the hair is now similar to that of adults. It is distributed as an inverse triangle pattern and spreads to the inner thighs, but not elsewhere above the base of the inverse triangle.	13.0–17.3

^aDerived from Marshall and Tanner.¹⁴