In the present study, we replicated and extended our previous findings of low urinary free-cortisol levels in PTSD. Cortisol was measured in 16 male patients (nine inpatients, seven outpatients) with posttraumatic stress disorder (PTSD) and in 16 nonpsychiatric control subjects. The mean cortisol level in the PTSD group was significantly lower, and the range narrower, than that observed in control subjects. Low cortisol in PTSD did not seem to be related to the presence or absence of major depressive disorder or to overall psychiatric symptomatology as assessed by the sum Brief Psychiatric Rating Scale score. In the outpatient group, there was a relationship between PTSD symptomatology and cortisol levels. The findings suggests a physiological adaptation of the hypothalamic-pituitary-adrenal axis to chronic stress.