The function of the hypothalamic-pituitary-adrenal axis as related to the degree of severity of a septic process was assessed by measuring plasma levels of beta-endorphin, ACTH and cortisol. Sixty-one cases of postoperative patients treated at the intensive care unit were classified into four groups according to the severity of infection: Group 1 (control) included patients who did not show any sign of infection, group 2 patients with sepsis, group 3 patients with septic syndrome and group 4 patients with septic shock. Compared to G1 patients' ACTH values (4.16+/-2.6pg/ml), a statistically significant increase in ACTH values in various stages of septicemia (p < 0.005) with a noticeable difference also between G3 (7.11 +/-3.7pg/ml) and G4 (11.5+/-6.6pg/ml) (p<0.05) was found. Differences were also observed in beta-endorphin (with a level of significance between the several groups of p = 0.0001). Also, beta-endorphin values in G4 (40.6+/-30.3 pg/ml) differed significantly from each of G1 (17.5 +/-6.6 pg/ml), G2 (21.1+/-11.3 pg/ml) and G3 (23.5+/-12 pg/ ml) (p<0.05). A progressive hypercortisolemia was obvious, with values of G4 (37.2+/-15.6 microg/dl) differing significantly from those of G1 (18+/-4.6microg/dl) and G2 (24-/+8.4microg/dl) (p<0.05) and of G3 (28.5+/-12.3 microg/dl) from that of G1 (p < 0.05). Interestingly, a dissociation of ACTH, beta-endorphin and cortisol was observed, in that the increased values of beta-endorphin and cortisol, detected in the G3 were not associated with a parallel increase in ACTH. These findings might be interpreted in the sense of an impairment of the stress stimulation of the hypothalamic pituitary adrenal axis. Provided that such a situation can be lethal, our results further confirm the idea that a low-dose, steroid replacement might be beneficial to critical illness.