Abstract Background: As a modifiable risk factor, physical activity (PA) has been linked to breast cancer, and there is cumulative evidence for a beneficial effect of PA on breast cancer risk. However, most of the studies were conducted in developed countries, with little knowledge on PA level and its relation to breast cancer risk among indigenous African populations, where breast cancer may have unique etiology. Methods: We used preliminary data from the African Breast Cancer Study (ABCS), a recently launched, multicenter case-control study, conducted in Cameroon, Nigeria, and Uganda in Africa. After consulting with native investigators in Africa, we developed a physical activity questionnaire to assess the type, frequency, intensity, and duration of various activities. Based on the questionnaire, we calculated sub-scores of housework PA, occupational PA, and leisure PA, as well as a total PA score estimating daily energy expenditure (MET-hours/day). Multivariate linear regression was used to examine the relationship between the total score and sub-scores of PA and case-control status, age, and study sites. Results: To date, 98 cases and 120 controls have been enrolled and the PA questionnaires were administered. The mean age was 48.6 years, ranging from 19-84 years. The overall PA score averaged at 29.6 MET-hours/day, mainly composed by housework PA (an average of 20.5 MET-hours/day) and occupational PA (an average of 16.2 MET-hours/day), with relatively low level of leisure PA (an average of 1.3 MET-hours/day). PA scores were the highest in the Cameroon study site, and the lowest in the Nigerian study site. PA score varied by age, but there was no clear trend. In the multivariable regression model, case-control status was significantly associated with the total PA score: cases were estimated to have 14.0 MET-hours/day lower PA compared to controls, after adjusting for age and study site (p<0.05). Conclusion: African women's physical activity mainly consists of housework activities and work-related activities, with little activities conducted for recreational purposes. The preliminary data show physical activity may be significantly associated with reduced breast cancer risk, but further investigation and a larger sample size are to be followed. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 674. doi:1538-7445.AM2012-674