Background: Sexually Transmitted Infections (STIs) have been shown to enhance the transmission of the Human Immunodeficiency Virus (HIV). The Hepatitis B and the Hepatitis C viral infections are highly prevalent among the HIV-infected persons as a result of shared transmission routes. Aim:To determine the seroprevalence of the HIV, Syphilis, HBV and HCV infections and their co-infection rates among Female Sex Workers (FSWs). Settings and Design: 250 blood samples were collected from FSWs from a red light area of Mumbai by using an outreach strategy. Materials and Methods:Their sera were tested for the HIV antibodies as per the strategy II of the NACO guidelines, for syphilis by RPR, for the HCV antibodies and for HBsAg by ELISA.