AbstractMillions of people in the United States are affected by sexually transmitted infections (STIs) every year, with profound consequences for the individual, their community, and society at large. In this review, we aim to summarize the epidemiology of 4 STIs: Chlamydia trachomatis, Neisseria gonorrhoeae, Treponema pallidum, and herpes simplex virus, and to highlight the consequences of those infections among individuals and the healthcare system. Untreated N. gonorrhoeae, C. trachomatis, T. pallidum, or herpes simplex virus infection can result in female infertility, stillbirth, premature birth, and low birth weight. As many as 10% of incident HIV infections among men who have sex with men in the United States have been attributed to either N. gonorrhoeae or C. trachomatis infection. In 1 year in the United States, incident C. trachomatis infection resulted in $824 million lifetime medical costs and a loss of 1,541 lifetime quality-adjusted life years (QALYs) among men and 111,872 among women, while incident N. gonorrhoeae infection led to $323 million in lifetime medical costs, and a loss of 386 QALYs among women and 12,112 among men. Incident T. pallidum infection in 1 year resulted in $206 million in medical costs and a loss of 13,349 QALYs among both men and women, while genital herpes led to $107 million in medical costs and a loss of 33,100 QALYs. STI-attributable infertility alone resulted in more than $135 million in direct medical costs. Cumulatively, STIs lead to substantial financial costs to individuals and the health system, as well as long-term reductions in quality of life.