A 9-year old female Shih Tzu dog was presented to the Veterinary Medical Teaching Hospital of Seoul National University with a history of chronic intermittent anorexia and vomiting of 4-year duration. She visited 3 years ago with the same clinical signs but has not been treated regularly due to waxing-waning course. On the physical examination, no specific findings were found. CBC, serum chemistry, radiography, ACTH stimulation test, evaluation of serum T4 and TSH concentration were performed. Hypoadrenocorticism was diagnosed with the ACTH stimulation test. And then, secondary hypoadrenocorticism was diagnosed with ACTH stimulation test, pre-ACTH aldosterone concentration, endogenous ACTH concentration. As electrolyte concentrations were normal, glucocorticoid (0.15 mg/kg bid PO) alone was administered. She has recovered from the clinical signs and has been doing well. It is suggested that the differentiation of secondary hypoadrenocorticism from primary hypoadrenocorticism is important as the secondary hypoadrenocorticism occurs rarely and the symptoms are non-specific with normal electrolyte concentrations.