A cusp catastrophe model of suicidal behavior with suicidal desire and suicidal capability, the two main dimensions of the interpersonal-psychological theory of suicide, serving as control parameters along the axes of the control surface. Suicide risk is represented on the vertical axis, and ranges from nonsuicidal to suicidal behavior. All possible combinations of desire and capability comprise the behavior surface. For most combinations of desire and capability, there is only one probable level of suicide risk, but within the boundaries of the bifurcation set, there are two probable levels (nonsuicidal and suicidal behavior) and one improbable level (suicidal planning). The interpersonal psychological theory’s four hypotheses describing the pathway to suicidal behavior are plotted on the control surface.