Introduction: Abnormal uterine bleeding (AUB) is the main cause of demand for gynecological care during the reproductive period, with negative consequences on women's lives. In Brazil, data on the prevalence of AUB is scarce and does not reflect the national reality. Objective: to evaluate the prevalence of AUB and associated factors in Brazil. Methods: Multicenter cross-sectional study, including 8 centers representing the 5 official geographic regions of Brazil. It included postmenarchal women who answered a sociodemographic questionnaire, with socioeconomic stratum and data related to uterine bleeding (self-perception of AUB and objective data) Results: 1928 women were included, with 35.5±12.5 years of age, 167 postmenopausal. The 1761 women in their reproductive period, had a menstrual cycle duration of 29.2±20.6 days, with bleeding for 5.6±4.0 days. In these, the prevalence of AUB, considering self-perception by the women, was 31.4%. Only among women who considered their bleeding abnormal, the menstrual cycle lasted less than 24 days in 28.4%, bleeding lasted longer than 8 days in 21.8%, 34.1% reported intermenstrual bleeding and 12.8% reported postcoital bleeding. Also, regarding these women, 47% reported a previous diagnosis of anemia, with 6% requiring intravenous treatment (iron or blood transfusion). Half of the women mentioned that the menstrual period had a negative impact on quality of life, while this worsening occurs in about 80% of those with self-perception of AUB. Conclusion: In Brazil, the prevalence of AUB is 31.4%, assessed by self-perception, in agreement with objective AUB parameters. The menstrual period has a negative impact on the quality of life of 8 out of 10 women with AUB.