Estimates of the global prevalence and incidence of sexually transmitted diseases in adolescents are limited. Recent prevalence estimates report over 333 million cases of the four major curable STDs in adults between the ages of 15 and 49: 12 million cases of syphilis, 62 of gonorrhoea, 89 of chlamydia, and 170 of trichomoniasis. The vast majority of these cases are in developing countries such as East Asia and Pacific, Sub-Saharan Africa, Latin American and Caribbean where syphilis and gonorrhoea still have a high prevalence. However, CT genital infection is the most commonly reported bacterial STD. In 1996 this infection had been the most common of the nationally notifiable infectious disease in the United States and was estimated that there were 2.5-3.3 million new cases per year. It resulted that African-American adolescents 14 to 19 years of age have the highest rates of STDs of any racial/ethnic group of adolescents. In addition, viral "non-curable" STDs have become a prominent public health issue over recent years due to a marked increase in prevalence of HSV and HPV infections. In the United Kingdom the annual number of genital herpes has almost tripled during the past 15 years. It is now evident that the high rate of HSV asymptomatic infection plays an important and complex role in estimating epidemiological data. To date, HPV genital infection probably represents the most frequent STD. The young age of sexual activity onset and lifetime number of sexual partners are considered the highest behavioral risk factors.