Stat Biosci DOI 10.1007/s12561-013-9079-8 CASE STUDIES AND PRACTICE ARTICLES A Statistical Perspective on Prevention Trials: A View from the Women’s Health Initiative Garnet L. Anderson Received: 5 June 2012 / Accepted: 7 January 2013 © International Chinese Statistical Association 2013 Abstract Chronic disease prevention trials test strategies to reduce the risk of a spe- cific health event in generally healthy people. These strategies are often thought to affect other health conditions and their use in the population requires a very favor- able safety profile. A prevention trial assessing such a strategy is most valuable when designed to capture the overall public health impact and hence provide more compre- hensive, reliable information for policy and practice. This broad agenda, and particu- larly the assessment of multiple outcomes, creates statistical challenges in the design, monitoring, and reporting of such a trial. In this article these issues are described in the context of the Women’s Health Initiative, a large randomized prevention trial test- ing three interventions in post-menopausal women: hormone therapy, a low-fat diet and calcium and vitamin D supplementation. Each intervention was hypothesized to influence multiple chronic disease rates including cardiovascular disease, stroke, can- cers, and fractures. Here the design, monitoring, and reporting of the WHI trials is reviewed in the context of multiple outcomes and the approach to a global assessment of these interventions is described. Keywords Multiple outcomes · Trial monitoring · Partial factorial design · Post-menopausal hormone therapy · Nutrition 1 Introduction 1.1 Prevention trials at the FHCRC Researchers in the Public Health Sciences Division of the Fred Hutchinson Cancer Research Center (FHCRC), under the direction of Dr. Ross Prentice, have established G.L. Anderson ( ) Women’s Health Initiative Clinical Coordinating Center, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave N M3-A140, Seattle, WA 98109, USA e-mail: garnet@whi.org