Injuries associated with hospitalization are more common in older (>/=65 years) than in younger patients (<65 years), and they may be more severe and more often preventable. The increasing age of the population magnifies the importance of this problem. In this review, we first consider medical injuries in general and then review the literature for 6 categories: adverse drug events, falls, nosocomial infections, pressure sores, delirium, and surgical and perioperative complications. For each of these categories, older patients appear to be at higher risk, ranging from a 2.2-fold increase for perioperative complications to a 10-fold increase for falling, based on Harvard Medical Practice Study rates. The main cause of these increased risks appears to be the diminished physiological reserve of elderly patients; however, age alone is a less important predictor of adverse events than comorbidities and functional status. Furthermore, many of these complications appear to be preventable, although the proportion preventable varies by type of complication. While some prevention strategies are specifically beneficial in older patients, many apply to all age groups. Geriatric care units and consultation systems have improved outcomes in some instances, although the data are mixed. The success of intervention varies by type of complications. For medications, various interventions have been successful, and fall prevention programs have been demonstrated to be effective in the nursing home and home.