Sexually transmitted diseases (STDs) are a major cause of morbidity and mortality in developing countries and may play a key role in enhancing the heterosexual transmission of human immunodeficiency virus (HIV). Treatment of STDs is one of the most cost-effective of all health interventions in developing countries; however, STDs among women in rural populations have received little attention. In this study, we report that prevalences of STDs among 964 women attending antenatal clinics in a rural area of the United Republic of Tanzania. A total of 378 (39%) of these women were infected with at least one STD pathogen, 97 (10%) had syphilis, and 81 (8%) has Neisseria gonorrhoeae (NG) and/or Chlamydia trachomatis (CT) infection. The recommended syndromic approach to screening for NG/CT infection, based on reported genital symptoms, had a low sensitivity (43%) and failed to discriminate between infected and uninfected women. A risk score approach that we developed, based on sociodemographic and other factors associated with NG/CT infection, had a higher sensitivity and lower cost per true case treated than other approaches, although its positive predictive value was only about 20%.