In 2010, almost 6,000 adults over age 65 died by suicide in the United States, and perhaps 200,000 worldwide. Because older adults are the most rapidly growing segment of the population, the number of suicides in this age group is expected to rise dramatically in coming decades. Development of effective approaches to late-life suicide prevention is a major public health priority. However, older adults pose particular challenges to prevention because self-injurious acts in later life tend to be more immediately lethal and with fewer warning signs than at earlier points in the life course. Research has delineated risk and protective factors in five domains: psychiatric illness (primarily mood disorders), personality and coping style, physical illnesses, social stressors and supports, and functional impairments. Research findings also indicate that primary care and other community-based health and human service settings are best suited to intervention implementation. Late-life suicide preventive interventions can be categorized as indicated (targeting high-risk individuals), selective (for individuals or groups with more distal risk factors), or universal (targeting a population) prevention approaches. Relatively few studies of preventive interventions that specifically target suicidal ideation, attempts, or completed suicide have been conducted in this age group. Available findings suggest that rates of suicidal ideation and behavior may be reduced by a variety of approaches. However, older women have been more responsive overall to preventive interventions than elderly men, the group at highest risk. Challenges remain to reducing suicide-related morbidity and mortality in later life.