With rates of gonorrhea and chlamydia on the rise in the US, this project seeks to understand the role of behavior change in these increased rates. Using data from the National Survey of Family Growth, this project is using epidemiologic and modeling approaches to describe patterns of changes in sexual behaviors, networks, and STI screening and to understand how these changes have contributed to increasing STI rates. The project focuses on cisgender heterosexual people ages 15-44 and describes differences in behaviors by sex, age, and race/ethnicity. It will develop a model of STI transmission that explores major components of behavior change among heterosexual populations over time.