An emerging literature suggests that posttraumatic stress disorder (PTSD) patients are at an increased risk for suicide. The objective of this study was: a) to reexamine the relationship between PTSD and suicide by comparing suicide risks of persons with PTSD, to persons with anxiety disorder and to matched controls; and b) to examine the relationship between anger, impulsivity, social support and suicidality in PTSD and other anxiety disorders. Forty-six patients suffering from PTSD were compared with 42 non-PTSD anxiety disorder patients and with 50 healthy controls on measures of anger, impulsivity, social support, and suicide risk. Persons with PTSD had the highest scores on the measures of suicide risk, anger, and impulsivity and the lowest scores on social support. Multivariate analysis revealed that in the PTSD group, impulsivity was positively correlated with suicide risk and anger was not. PTSD symptoms of intrusion and avoidance were only mildly correlated with suicide risk at the bivariate level but not at the multivariate level. For the PTSD and anxiety disorder groups, the greater the social support, the lower the risk of suicide. For the controls, social support and impulsivity were not related to suicide risk, whereas anger was. These findings suggest that persons with PTSD are at higher risk for suicide and that in assessing suicide risk among persons with PTSD, careful attention should be paid to levels of impulsivity, which may increase suicide risk, and to social support, which may reduce the risk.