In the United States, young people aged 15-24 represent 25% of the sexually experienced population. In this study, Data from a variety of sources are used to estimate the incidence and prevalence of STDs among 15-24-year-olds in the United States in 2000. The quality and reliability of the estimates are categorized as good, fair or poor, depending on the quality of the data source. The results show that approximately 18.9 million new cases of STD occurred in 2000, of which 9.1 million (48%) were among persons aged 15-24. Three STDs (human papillomavirus, trichomoniasis and chlamydia) accounted for 88% of all new cases of STD among 15-24-year-olds.