A seroepidemiologic survey was performed aimed at estimating the prevalence of human immunodeficiency virus, the prevalence of hepatitis C virus antibodies (anti-HCV), the risk factors associated with human immunodeficiency virus transmission and the epidemiological profile of the women in puerperal period in three public Hospitals of Cuiabá City between December 2001 and March 2002. The sample was composed of 1,607 women who were interviewed in order to obtain information about socio-demographic aspects and risk behavior. Blood samples were drawn to detect HIV and HCV antibodies using the ELISA test. The prevalence of HIV infection in this population was 0.5% (IC95%= 0.2; 1.0). Most women had only basic level schooling (58.4%), and they presently held a relationship with a fix partner (73%). There were no statistically significant associations between HIV antibody and socioeconomic level, other procedures that involved the risk of HIV parenteral transmission, between anti-HIV positivity and the presence of sexual behavior of risk (relationships with multiple partners or bisexuality) by the women and their partners. Currently, it is presumed that heterosexual transmission is the main cause of infection among women in reproductive age in the study area. The anti-HCV prevalence was 0.4% (CI95%= 0.1; 0.8). Anti-HCV was more common among older women.