(“Women’s Health Initiative”, NIH/NHLBI). The WHI, an ongoing 25-year national health study conducted at 40 clinical centers across the U.S., has focused on strategies for preventing heart disease, breast and colorectal cancer, and osteoporotic fractures in postmenopausal women. Dietary data at multiple time points were collected from two WHI components: WHI Dietary Modification Trial (DMT) and OS. Women were on average 65 years (min.: 49y; max: 81y) old upon enrollment, with most (70.1%) having more than a high school education. The FFQ was developed with measurement characteristics assessed. All women in the DMT completed the FFQ at baseline and about 92% completed it at year 1. After that, a rotating sample of one-third of the women (N≈16,000) completed the FFQ annually. Additionally, a 6% cohort of DMT participants (N≈2900) provided detailed 4-day food records at baseline and year 1. At years 3, 6, and 9, dietary assessment continued with two 24-h dietary recalls on nonconsecutive days replacing the 4-day food records. All WHI OS participants completed a baseline FFQ and about 90% also completed it at Year 3.