The Monitoring STIs Survey Program (MSSP) monitored sexually transmitted infection (STI) prevalence among probability samples of adolescents and young adults aged 15 to 35 with landline phones in Baltimore, Maryland from 2006 to 2009. The MSSP collected survey data using telephone audio computer-assisted self-interviewing (TACASI) and biospecimens which were tested using nucleic acid amplification tests to monitor trichomonaiasis and other STIs. Respondents provided information about their sexual practices, sexual history, information about incarceration of themselves or their partners, and information about sexually transmitted diseases (STDs), STIs, and respective treatments. Demographic variables collected include gender, race, educational attainment, age, employment status, and marital status.