Athletic training in adolescent females is important for their well-being; indeed, it may have both positive and negative effects on some physiological processes, as growth, reproductive axis and bone health. Adequate physical activity likely exerts neither a positive nor a negative effect on growth. By contrast, intensive training and insufficient diet may have a negative influence on growth, probably due to energy deficiency and impairment of the growth hormone-insulin-like growth factor-I axis; net long term-effects of such alterations remain to be established. Adolescents who perform regular athletic training present with normal or slightly advanced sexual maturation, because increased strength and power associated with earlier maturation advantage them. However, intensive training and inadequate energy intake may induce delayed menarche and menstrual dysfunctions. The consequent hypoestrogenism, in association with the nutritional deficiencies, may affect bone health. On the contrary, regular physical activity increases the amount of bone mass gained during childhood and adolescence mainly at the bone sites which are trained. Since the number of adolescent females involved in strenuous sports from an early age is increasing, physicians must be aware of such effects, explain to girls and their parents the 'right' sports training and appropriate dietary regimens, and recognize problems due to excessive training as soon as possible. These issues should not be a cause of lesser involvement in athletic participation of young people.