MultIethNic Study of BrEast ARterial Calcium Gradation and CardioVAscular Disease (MINERVA) was designed to answer the question of whether a novel continuous breast arterial calcification (BAC) mass score improves cardiovascular risk stratification among asymptomatic postmenopausal women. This article describes recruitment and baseline characteristics. MINERVA is a multiethnic longitudinal cohort study. The phenotype data include BAC mass by densitometry applied to digital mammograms, sociodemographic factors, self-reported medical history, medications, parental history, reproductive history, smoking, alcohol consumption, physical activity, anthropometry, ankle-brachial index, blood pressure, laboratory panel, breast volumes, cognitive function, bioelectrical impedance, habitual diet, dietary supplements, sleep, psychosocial factors, and sun exposure. A total of 5145 women aged 60 to 79 years with available digital, uncompressed mammograms were recruited from the membership of Kaiser Permanente of Northern California between October 24, 2012 and February 13, 2015 and completed a baseline clinic visit or an abbreviated phone questionnaire. Of those, 4153 underwent phlebotomy and have blood biomarkers. Overall prevalence of BAC was 26%, and it varied by age and race. The mean (SD) BAC mass was 12 (23) mg and the range 0-342 mg. MINERVA is the first cohort with a continuous measure of BAC. The cohort is large, ethnically diverse, and deeply phenotyped in terms of socioeconomic, behavioral, and clinical factors, and blood biomarkers.