More than a quarter of the world'spopulation is between the ages of 10 and 24. Most (86percent) of the world's 1.7 billion young people livein developing countries, where they are often 30 percent ormore of the population. At first glance, youth appears to bea relatively healthy although not hazard-free period oflife. Young people account for 15 percent of the disease andinjury burden worldwide and over one million die each year,mainly from preventable causes. Nonetheless, roughly 70percent of premature deaths among adults can be linked tobehavior initiated during adolescence, such as tobacco use,poor eating habits, and risky sex. Investing in health anddevelopment of young people is not only the right thing todo, it's the smart thing for countries that want theireconomies to grow faster: 1) reducing HIV infection in youngpeople will reduce the devastating economic impact ofHIV/AIDS; 2) when young people postpone marriage andchildbearing, family size falls and population growth slows.Combined with investments in health and education, thesechanges contribute to higher economic growth and incomes;and 3) investments to head off negative behaviors such astobacco use and drug abuse will pay off later forindividuals and for society.