Severe hyponatremia, defined by a sodium concentration of below 115 meq/l, is rarely reported with Schmidt's syndrome. We report a 43-year-old woman diagnosed with Schmidt's syndrome during the workup for severe hyponatremia as well a review of all the reported cases. The Medline database from 1960 to 2007 and relevant references of selected articles were searched. Search terms included hyponatremia, hypothyroidism, autoimmune thyroid disease, adrenal insufficiency, adrenal failure, Schmidt's syndrome and autoimmune polyendocrine syndrome type 2. The search was restricted to the English language, human subjects, and patients with a serum sodium concentration of below 115 meq/l. Seven cases were reported including this report. Severe hyponatremia seems to be found more often in patients with severe hypothyroidism. To our knowledge this is the first case to describe the occurrence of severe hyponatremia with normal thyroid function test and normal baseline cortisol level.