Most individuals who consider suicide do not make suicide attempts. It is therefore critical to identify which suicide ideators are at greatest risk of acting on their thoughts. However, few seminal theories of suicide address which ideators go on to make attempts. In addition, perhaps surprisingly, most oft-cited risk factors for suicide-such as psychiatric disorders, depression, hopelessness, and even impulsivity-distinguish poorly between those who attempt suicide and those who only consider suicide. This special section of Suicide and Life-Threatening Behavior serves to highlight this knowledge gap and provide new data on differences (and similarities) between suicide attempters and suicide ideators. © 2013 The American Association of Suicidology.