Despite concerted research efforts to understand causes and consequences of adverse medical events, sometimes referred to as medical injuries, a paucity of information exists about the scope and impact of adverse medical events over time, especially among older adults. Moreover, because previous research has focused primarily on acute care settings, little is known about the pattern of adverse medical events across healthcare settings. In response, the overall goal of this project is to conduct a nationally representative, longitudinal investigation of the incidence of adverse medical events among older adults and examine the subsequent patterns of health, healthcare service use, and costs over several years duration. To achieve our project goal, the following four, specific aims will guide research activities: (1) Examine the incidence and patterns of sentinel adverse medical events among older adults across settings and over time. (2) Examine the consequences of sentinel adverse medical events on subsequent healthcare service use over time. (3) Explore transitions in health and functioning levels over time. (4) Estimate the direct and indirect healthcare costs associated with sentinel adverse medical events over several years of study. We will draw upon multiple years of the Medicare Current Beneficiary Survey (MCBS), a nationally representative, longitudinal panel of Medicare beneficiaries, to build an analytical data file capable of tracking adverse medical events across medical settings and over time for five separate cohorts of Medicare beneficiaries. Descriptive and multivariate techniques will be used to explore longitudinal trajectories of health, functional status, service use and costs of older adults experiencing an adverse medical event. Hazard models will be estimated to explore the long-term effect of adverse medical events on the risk of nursing home entry, hospitalization or death. Multivariate transition models will be estimated to investigate the effect of adverse medical events on subsequent transitions between health status states and physical functioning levels over time. Findings from this research are expected to provide new insight into the scope and complexity of adverse medical events among older adults by adding to the existing literature in several innovative ways. First, we will extend previous research efforts in new directions by exploring both the direct and indirect impact of adverse medical events on outcomes over time. Second, we will develop a comprehensive approach to measuring both the incidence and impact of adverse medical events by creating windows of observation that extend beyond a single setting or medical episode. Third, our use of longitudinal methods will allow us to explore the extent to which individual, behavioral and environmental factors affect outcomes. And fourth, findings from our study will provide critical insight into the efficiency of the healthcare system by examining the burden of adverse medical events and providing a strong, empirical foundation to guide future studies. Public Health Relevance: This study will identify risk factors of and long-term consequences following adverse medical events among older adults. Findings will assist ongoing efforts to identify and prevent medical injuries. The study addresses the Institute of Medicine's To Err is Human objective to reduce medical injuries as well as the Healthy People 2010's objectives to improve patient safety and reduce injuries.