Background: In Kenya, sexually transmitted disease (STD) clinics care for large numbers of patients with STD-related signs and symptoms. Yet, the etiologic fraction of the different STD pathogens remains to be determined, particularly in women. Goal: The aim of the study was to determine the prevalence of STDs and of cervical dysplasia and their risk markers among women attending the STD clinic in Nairobi. Study Design: A cross-section of women were interviewed and examined; samples were taken. Results: The mean age of 520 women was 26 years, 54% had a stable relationship, 38% were pregnant, 47% had ever used condoms (1% as a method of contraception), 11% reported multiple partners in the previous 3 months, and 32% had a history of STDs. The prevalence of STDs was 29% for HIV type 1, 35% for candidiasis, 25% for trichomoniasis, 16% for bacterial vaginosis, 6% for gonorrhea, 4% for chlamydia, 6% for a positive syphilis serology, 6% for genital warts, 12% for genital ulcers, and 13% for cervical dysplasia. Factors related to sexual behavior, especially the number of sex partners, were associated with several STDs. Gonorrhea, bacterial vaginosis, cervical dysplasia, and genital warts or ulcers were independently associated with HIV infection. Partners of circumcised men had less-prevalent HIV infection. Conclusion: Most women reported low-risk sexual behavior and were likely to be infected by their regular partner. HIV and STD prevention campaigns will not have a significant impact if the transmission between partners is not addressed.