Previous research documented the elevated risk of suicide and suicidal ideation among Vietnam veterans with post-traumatic stress disorder (PTSD). The aim of the current study was to examine which Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, PTSD symptom clusters are most associated with suicidal ideation in this population. Fifty Vietnam combat veterans enrolled in treatment for PTSD responded to the Beck Scale for Suicide Ideation and were interviewed with the Clinician-Administered PTSD Scale. In linear regression analysis, it was found that the reexperiencing symptom cluster was significantly associated with suicidal ideation but the other two symptom clusters (avoidance/numbing and increased arousal) were not. Furthermore, scores on a measure of severity of combat exposure were not found to be significantly related to PTSD symptoms or suicidal ideation. The results of this study suggest the importance of reexperiencing symptoms for predicting which individuals with combat-related PTSD are most at risk for suicidal ideation and behavior.