Summary. Data on pregnancy, abortion, sexually transmitted disease and cervical dysplasia in girls under the age of 16 years were collected from British and American publications. Over half the pregnancies in girls under 16 ended in induced abortion, and those that continued had increased maternal and perinatal mortality, partly due to failure to attend for care. A prospective study in young teenagers found a high rate of fetal loss in pregnancies that followed abortions. Apart from an increased risk of cervical injury, abortion in girls under 20 carried the same risk of complications as for the American population as a whole. The risk of developing carcinoma of the cervix was doubled in women who began sexual activity before the age of 17 and a large survey found that 1.9% of the girls aged between 15 and 19 years had abnormal cervical cytology. Discouraging sexual activity before the age of consent seems to have a medical as well as a moral basis.