Ninety male Vietnam veterans with posttraumatic stress disorder (PTSD) were administered relaxation instructions, relaxation instruction with deep breathing exercises, or relaxation instructions with deep breathing training and thermal biofeedback. Improvement appeared on only 4 of the 21 PTSD and physiological dependent variables studied. All 21 Treatment x Time interactions were nonsignificant. This suggests that the treatments were mildly therapeutic, but that the additions of training in deep breathing and thermal biofeedback did not produce improvement beyond that associated with simple instructions to relax in a comfortable chair.