Adrenal insufficiency is known to be a complication of HIV infection, although estimates of its prevalence and severity vary. Adrenal insufficiency is the most serious endocrine complication that occurs in persons with HIV infection. Patients with acquired immune deficiency syndrome (AIDS) are considered to be at high risk for primary or secondary adrenal insufficiency. We describe 3 patients with AIDS who had clinical features suggestive of adrenal insufficiency, but their corticotropin (ACTH) stimulation tests were normal. Repeat testing confirmed the diagnosis in one patient, and further testing with the overnight metyrapone test revealed evidence of secondary adrenal insufficiency in the other patients. Persistent clinical improvement was evident on subsequent glucocorticoid therapy. A normal response to the ACTH stimulation test can be dangerously misleading. Patients with AIDS and suspected adrenal insufficiency who have normal screening by the ACTH stimulation test should undergo further testing for secondary adrenal disease.