Often long-term low-dosage glucocorticoid therapy cannot be terminated. This is due to the fact that even low doses which are within the physiological replacement range can cause a detectable, though clinically insignificant suppression of the adrenal gland function, resulting in "corticosteroid withdrawal syndrome". Another reason is the fact that it is necessary to be able to suppress undesirable inflammatory reactions caused by the underlying disease. ACTH testing of the adrenal capacity is widespread, but repeated testing may lead to undesirable side effects, such as allergic reactions. This study investigates the usefulness of testing the function of the pituitary-adrenal axis in predicting withdrawal problems. In 21 patients with chronic inflammatory disease who were treated with glucocorticoid doses of 5 to 10 mg prednisolone equivalent daily for a period of 2 to 131 months, stimulation with 100 microg hCRH (human corticotrophin-releasing hormone) was performed prior to the gradual withdrawal of medication. Blood samples were taken at baseline and after 45 minutes to measure ACTH and cortisol levels. Four weeks after steroid withdrawal the patients were reevaluated for signs of a relapse of the underlying disease in order to establish the necessity of reintroducing steroid therapy. This reevalution comprised clinical criteria, laboratory tests and the patients' own assessment of his/her well-being. In sixteen patients who later successfully withdrew from glucocorticoid therapy, a significant increase in cortisal levels was noticed after stimulation with CRH (p < 0.05). In five patients, with whom steroid withdrawal was not successful, baseline levels of cortisol were significantly lower than in the others (p < 0.05) and no sufficient increase was achieved after stimulation with CRH. These results show that successful withdrawal of a long-term low-dosage glucocorticoid therapy depends on the integrity of the pituitary-adrenal axis. Therefore CRH testing for evaluation of the pituitary-adrenal axis can be helpful in identifying patients in whom glucocorticoid withdrawal would be troublesome.