Introduction: A large proportion of deaths and many illnesses can be attributed to three modifiable risk factors: tobacco use, overweight/obesity, and physical inactivity. Health risk assessments (HRAs) are widely available online but have not been consistently used in healthcare systems to activate patients to participate in prevention programs aimed at improving lifestyle behaviors. Objectives: The goal of this study is to test whether adding telephone-based coaching to use of a comprehensive HRA increases at-risk patients' activation and enrollment into a prevention program compared to HRA use alone. Methods: Participants were randomized to either complete an HRA alone or in conjunction with a telephone coaching intervention. To be eligible Veterans had to have at least one modifiable risk factor (current smoker, overweight/obese, or physically inactive). The primary outcome is enrollment and participation in a prevention program by 6 months. Secondary outcomes include change in a Patient Activation Measure and Framingham Risk Score. Discussion: This study is the first to test a web-based health risk assessment coupled with a health coaching intervention within a large healthcare system. Results from this study will help the Veterans Health Adininistration (VHA) implement its national plan to include comprehensive health risk assessments as a tool to engage Veterans in prevention. The results will also inform health systems outside VHA who seek to implement Medicare's advisement that health risk assessment become a mandatory component of care under the Affordable Care Act. Published by Elsevier Inc.