Background In the Netherlands no guidelines exist for routine STI screening of HIV-infected patients. In a study in two academic hospitals in the Netherlands, 16% of HIV-infected MSM in HIV care had an asymptomatic STI, making regular STI screening in this group appropriate. It is unclear whether regular STI screening should also be considered for HIV-infected heterosexual men and women. Therefore, we studied the prevalence of, and factors associated with asymptomatic STI in a representative group of HIV positive heterosexual men and women. Methods HIV-1 infected heterosexual patients visiting the HIV outpatient clinic of the Academic Medical Center in Amsterdam, the Netherlands, were screened for STI during a routine visit. Patients spontaneously reporting symptoms compatible with STI were excluded. Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) were tested by PCR on throat swabs, vaginal or anal self swabs and urine samples, depending on gender and sexual behaviour. Hepatitis B virus (HBV) and hepatitis C virus (HCV) serology were performed and patients were screened for syphilis by TPHA and RPR. Participants were interviewed by a trained interviewer about sexual risk behaviour in the previous 6&emsp14;months. Results Between October 2007 and June 2008, 248 men and women (median age 41&emsp14;years, range 18–82) were included. 56% was female and 42% had Dutch ethnicity, the main other ethnicities were Ghanese, Surinamese/Antillean and Sub-Saharan African. <cross-ref type="tbl" refid="tbl1">The Abstract P1-S5.27 table 1</cross-ref> shows sexual behaviour of participants in the preceding 6&emsp14;months. Reported history of STI in the last 6&emsp14;months was 2%, and lifetime history of STI (non-HIV) was 49%. 29% of participants had had STI testing in the preceding 6&emsp14;months, and 64% had an STI test more than 6&emsp14;months ago. Only four patients (1.6%) had an asymptomatic STI. Two women were diagnosed with vaginal CT, 1 man with urethral CT and a female ...