A girl who is healthy, has no symptoms or history of gynecologic problems, has not started her periods yet, or is having routine menstrual cycles, and has not started to have sexual activity, does not really need to have a pelvic exam until college age.
A teenager who has already started to have sexual intercourse should have a gynecological exam and Pap smear. This evaluation will also include screening for sexually transmitted diseases, and education about prevention of these diseases, as well as education about preventing pregnancy. Early sexual activity does put a young woman at higher risk for cervical cancer, so it is important that a full examination is done.
Teenagers who have had any history of menstrual problems (not just cramps), should also be evaluated to make sure there are no structural problems or hormonal abnormalities present.