In most cultures sexually transmitted diseases (STD) and unwanted pregnancy are major health problems for sexually active youths aged 15-24. Since the early 1970s contraceptive use has increased in developed countries, but as few as 4-6% of young people in developing countries have access to reliable, modern contraceptives. In most countries the age-specific rates for STD are highest in the younger age groups. One of the few methods available to limit the extent of these problems, and particularly the problem of infection with human immunodeficiency virus (HIV) and acquired immunodeficiency syndrome (AIDS), is health education directed toward behavioral change. The content, timing, and characteristics of the source presenting the information are all important. This article reviews international data on the problems of STD and AIDS in young people and the experience of various countries in preventive efforts through health education.