girls, the first sign of puberty is the onset of breast development (thelarche) which occurs at a mean age of approximately 11 years; this is followed by pubic hair growth and menarche. In boys, the first sign is testicular enlargement which occurs at a mean age of approximately 11.5 years; this is followed by penile and pubic hair growth. In The diagrams above demonstrate the sequence of events at puberty. An average boy and girl are represented in relation to the scale of ages. The range of ages within which some of the changes occur is indicated by the figures below them. Data from Marshall, WA, Tanner, JM. Arch Dis Child 1969; 44:291.