We propose to continue the largest follow-up study of the health of African-American women yet undertaken, the Black Women's Health Study (BWHS). The aim is to determine the effects on breast cancer incidence (and eventually other cancers) of potential risk factors, including physical activity, obesity, alcohol, diet, oral contraceptives, and postmenopausal female hormones. Most of these factors have not been studied in black women. In addition, factors specific to African-American women, including experiences and perceptions of racism and use of hair straightening products (which is very common) will be assessed. Because prevention programs require an understanding of the determinants of risk factors, we will also assess correlates of important risk factors. The BWHS cohort was established in 1995 when 64,554 black women aged 21-69 years from all regions of the U.S. completed mail questionnaires, providing data on demographic factors, medical and reproductive history, use of oral contraceptives and other drugs, physical activity, smoking, alcohol use, diet, and other factors. Methods for following participants, collecting, processing and managing the data, and validating cancer outcomes have been developed, and results of analyses of the baseline data have been published. The first round of follow-up (every 2 years) to determine incident cancer and changes in exposures has been carried out, with a follow-up rate of 83 percent. After further cycles of follow-up through the end of the proposed grant, 600 plus cases of breast cancer will be available for analysis. Hypotheses to be assessed include whether physical activity reduces the incidence, and whether dietary fat intake and alcohol consumption increase it. African-American women suffer a greater burden of cancer morbidity than white women but there have been few studies in black women. The BWHS will contribute to the effort to improve the health of African-American women by providing insight into causes and preventives of breast cancer and other cancers and useful information for intervention programs.