Sexually transmitted infections (STIs) represent a major global health problem leading to morbidity, mortality and stigma. Prior to this study there was no information on the prevalence and knowledge of STIs in Faisalabad, Pakistan.Prospective, cross-sectional study in patients attending STI clinics from July 2006 to September 2009.After obtaining consent, patients completed structured questionnaires used for behavioral surveys. Blood and urethral swabs were collected and tested for syphilis, gonococcus, genital herpes, chlamydia and chancroid.Mean (standard deviation) age of the 1532 participants was 38.9 (9.4) years, including 37.8 (10.2) years for males and 35.5 (6.3) years females. Male gender (n=1276, 83.3%), low socioeconomic class (n=1026, 67.0%) and residence in rural suburbs (n=970, 63.3%) were more common. Most (n=913, 59.6%) were aware of the modes of transmission of STIs and the associated complications, 20% (n=306) were condom users, and 21.2% (n=324) had knowledge of safe sex. Opposite-sex partners were preferred by 972 (63.4%) patients, while 29.9% (n=458) had both homosexual and heterosexual sex partners. Syphilis was present in 29.5% of patients (n=452); gonorrhea, in 13% (n=200), HSV-2, in 3.2% (n=49), chlamydia, in 4.7% (n=72) and chancroid, in 1.3% (n=20).This report establishes baseline local prevalence rates for STIs. Syphilis emerged as the most prevalent STI in Faisalabad. Population-based studies are required to study the epidemiology of STIs, along with initiation of national health-education campaign.