Eleven girls treated during childhood for acute leukaemia were followed up during their pubertal development. At each examination weight, height, pubertal stage, FSH, LH, oestradiol, testosterone, androstenedione and dehydroepiandrosterone sulphate levels were evaluated. Clinical and endocrinological studies were performed according to age and pubertal stage and compared to those of healthy girls matched for age and pubertal stage. Results showed that pubertal maturation and gonadal function were not affected by oncotherapy; however menarche was attained earlier. Early menarche was explained by the overweight of treated girls during early puberty. No evidence of early hypothalamic activation was found, but endocrine patterns showed a faster hypothalamopituitary-ovarian axis maturation in patients than controls. Cranial irradiation showed no correlation with pubertal onset and age at which menarche was attained. Adolescent menstrual and endocrine patterns were normal.