Suicidal behavior ranges in degree from merely thinking about ending one's life through developing a plan to commit suicide and obtaining the means to do so, attempting to kill oneself, to finally carrying out the act ("completed suicide"). A section on the extent of the problem encompasses both suicidal behavior and nonfatal suicidal behavior and ideation. The risk factors for suicidal behavior encompass psychiatric factors, biological and medical markers, life events as precipitating factors, and social and environmental factors. The chapter advises that risk factors for suicidal behavior are numerous and interact with one another. Knowing which individuals have a predisposition to suicide, and also possibly face a combination of risk factors, can help pinpoint those most in need of prevention efforts. Efforts to prevent suicides encompass treatment approaches, which can include the treatment of mental disorders and pharmacotherapy; behavioral approaches, which include behavioral therapy and "green" cards (gives client direct and immediate access to a range of options, such as an on-call psychiatrist or hospitalization); relationship approaches, which involve psychosocial interventions; community-based efforts (suicide prevention centers and school-based interventions); and societal approaches, which can include restricting access to suicide means and media reporting. Intervention after a suicide can include support groups for those impacted by the suicide. Recommendations pertain to better data, further research, better psychiatric treatment, environmental changes, and the strengthening of community-based efforts. "Boxes" within the chapter present brief discussions of suicide among indigenous peoples in Australia and Canada and depression and suicide. 1 table and 183 references