ObjectivesTo assess the relationship between hormone replacement therapy (HRT) and coronary artery calcium (CAC). DesignCross-sectional. SettingEstablished population-based cohort in Reykjavik, Iceland. ParticipantsWomen (mean age 76 5) who had completed questionnaires on HRT use (N = 2,867). MeasurementsCoronary artery calcium assessed using computed tomography was the outcome variable and was compared between women with history of HRT and those who had never used HRT and analyzed according to age, length of use, and time after menopause that HRT was initiated. ResultsEight hundred seventy-two (30.4%) participants had used HRT, and 312 (10.9%) were current users. After adjustment for age, other late-life variables, and a propensity score based on midlife data for HRT use as observed in late life, there were significant negative associations between CAC and history and length of HRT use. This association was evident in all age categories. When HRT had been used for longer than 15 years, median CAC level was less than 50% of that observed in never users. The lowest CAC was observed in those who started HRT within 5 years after menopause. The prevalence of coronary events was comparable in both groups. ConclusionA strong association was found between long-term HRT use and low CAC. The negative association between duration of HRT and CAC was evident in all age groups of older women.