Adrenocortical function in patients with active pulmonary tuberculosis is a debate of matter. Previous studies related to adrenocortical function in patients with active pulmonary tuberculosis demonstrated a high rate of suboptimal cortisol response to standard dose ACTH (250 microg) stimulation test. The aim of this study was to assess the hypothalamo-pituitary-adrenal (HPA) axis in low dose (1 microg) and standard dose ACTH (250 microg) stimulation tests in the patients with active pulmonary tuberculosis. Twenty-seven patients and 21 healthy subjects were included in the study. Cortisol levels were measured before, 30 and 60 min after ACTH (1 microg or 250 microg iv) injection. Cortisol responses to 1 microg ACTH at 30 and 60 min were significantly higher in the patient group than in the control group (p<0.05). Peak cortisol levels were significantly higher in the patient group than in the control group after both 1 microg and 250 microg ACTH administration (p<0.05). Cortisol responses to 250 microg ACTH at 30 and (at 30 and 60) 60 min were significantly higher in the patient group than in the control group (p<0.05). Peak cortisol levels obtained after 250 microg ACTH and after 1 microg ACTH were similar in the patient group (p>0.05). This study shows that 1 microg ACTH iv gives an equivalent peak cortisol value to 250 microg ACTH in patients with activated HPA axis. The cortisol levels obtained at 08:00, 11:00, 17:00 and 24:00 h were significantly higher in the patients than in the controls. This study clearly shows that HPA axis is activated in active pulmonary tuberculosis rather than underactivated.