BACKGROUND: Screening mammography for women 50 to 69 years of age may lead to 50% having an abnormal study. We set out to determine the proportion of women who understand their abnormal mammogram results and the factors that predict understanding. METHODS: We surveyed 970 women age 40 to 80 years identified with abnormal mammograms from 4 clinical sites. We collected information on demographic factors, language of interview, consultation with a primary care physician, receipt of follow-up tests, and method of notification of index mammogram result. This study examines the following outcomes: the participant’s report of understanding of her physician’s explanation of results of the index mammogram, and a comparison of the radiology report to the participant’s report of her index mammogram result. Multivariate models controlled for age, education, income, insurance status, and clinical site. RESULTS: The majority (70%) reported a ‘‘full understanding’’ of their physician’s explanation of their abnormal mammogram, but a significant minority (30%) reported less than a full understanding (somewhat, not at all, did not explain). Among women of Asian ethnicity, only 63% reported full understanding. Asian ethnicity was a negative predictor (odds ratio [OR], 0.4; 95% confidence interval [CI], 0.3 to 0.7), and consultation with a primary care physician was a positive predictor (OR, 2.3; 95% CI, 1.7 to 3.3) of reported full understanding. Of the 304 women with a suspicious abnormality, only 51% understood their result to be abnormal. Women notified in person or by telephone were more likely than women notified in writing to understand their result to be abnormal (OR, 2.3; 95% CI, 1.2 to 4.8). CONCLUSION: Almost half of women with the most suspicious mammograms did not understand that their result was abnormal. Our data suggest that direct communication with a clinician in person or by phone improves comprehension.