OBJECTIVES: Despite consistent sexually transmitted infection (STI) screening guidelines for asymptomatic women, less than half of women age 25 and younger are being tested for chlamydia trachomatis (CT) and neisseria gonorrhea (NG).  This study sought to understand how physicians determine which patients to screen and the perceived barriers to screening. METHODS: Sixty semi-structured, 45-min phone interviews were conducted from a nationally representative sample of 30 Obstetric-Gynecologists (OBGyns) and 30 Family Practitioners (FPs). Respondents were recruited if they had 5-30 years of experience and reported that they sometime, often or always perform STI testing.  A thematic approach was used to analyze the data. RESULTS: Approximately 1 in 4 FPs offer STI testing only to symptomatic patients.  OBGyns were more likely to screen based solely on age.  However, approximately half of all interviewees used age in conjunction with a clinical risk assessment to determine which patients to offer screening.  The most frequently sited barriers to screening for STIs were: Patients not wanting the tests, Patients not seeking regular care, Parents or partners present in the room, Patient anxiety/embarrassment, and Patient cost concerns. The majority of respondents (75%) felt lab algorithms that automated the STI testing based on screening criteria would be helpful.   CONCLUSIONS: Most physicians selectively offer STI screening to women based on age and a risk assessment, with patients opting-in by specifically saying they want STI screening.  The adopting of automated STI testing with an opt-out option for women age 15-25  would help reduce inconsistencies in physician’s test ordering, align practice with clinical guidelines, reduce stigma associated with STI testing, and increase the rate of patient acceptance by overcoming some of the barriers to screening.