OBJECTIVE: Decreased cardiac vagal control (CVC) has been proposed in posttraumatic stress disorder (PTSD), but the results are mixed. Analyses with larger sample sizes and better methodology are needed. METHODS: Thirty-two drug-naive survivors with current PTSD, 32 survivors without PTSD and 192 matched controls were recruited for a case-control analysis. We used the PTSD checklist-civilian version (PCL-C) to assess posttraumatic symptoms severity. Cardiac autonomic function was evaluated by measuring heart rate variability (HRV) parameters. Frequency-domain indices of HRV were obtained. The obtained results were evaluated in association with personality traits assessed by the Tridimensional Personality Questionnaire (TPQ). RESULTS: PTSD patients exhibited decreased LF-HRV and HF-HRV as compared to survivors without PTSD and to matched controls. The PTSD symptoms severity was associated with reduced mean RR intervals, Var-HRV, LF-HRV and HF-HRV. The harm avoidance score (which has been suggested to be associated with serotonergic activity) was negatively correlated with Var-HRV, LF-HRV and HF-HRV. CONCLUSION: These data suggest that PTSD is accompanied by decreased CVC, highlighting the importance of assessing HRV in PTSD patients. In view of the increased risk for cardiovascular diseases in these vulnerable individuals, one might consider the treatment to restore their autonomic function while reducing PTSD symptoms.