By age 15, most girls have had their first menstrual period and have completed the rapid growth spurt that usually occurs during puberty. After the first period, teenage girls grow 1.5 in. (3.8 cm) to 3 in. (7.6 cm) on average. Other early changes of puberty, such as the growth of pubic hair and breasts, have also occurred. Teenage girls tend to complete breast development an average of 4 years after breast buds signal the beginning of puberty.

The growth spurt in boys tends to reach its peak sometime during the early to mid-teen years. Although boys lag behind girls in height in early adolescence, they generally end up being taller than girls by age 18. After growth starts, boys grow at a faster rate and for a longer period of time. Also, boys usually continue growth of facial hair, penis and testicles, and pubic hair during the late teen years.

These and other physical changes are highly variable by individual. Some individuals are "early bloomers," and others grow and develop later.