Factors that determine a post-menopausal woman's bone mineral density (BMD) include her mass at the time of skeletal maturity (peak BMD), menopause and the rate of loss she experiences as she ages. Understanding the relative influence of each of these factors may help identify important preventive treatments and provide new ways to identify women at risk for osteoporosis. In this analysis we utilize a computer model of the bone remodeling process to predict the relative influences of peak BMD, menopause and age-related bone loss on the development of osteoporosis. The delay in the onset of osteoporosis (defined as BMD <2.5 SD from the young adult mean) caused by modifying peak BMD, age-related bone loss or the age at menopause is quantified. A 10% increase in peak BMD is predicted to delay the development of osteoporosis by 13 years, while a 10% change in the age at menopause or the rate of non-menopausal bone loss is predicted to delay osteoporosis by approximately 2 years, suggesting that peak BMD may be the single most important factor in the development of osteoporosis.