—To the various types of urinary calculi usually described in the literature Braasch1 added another form of lithiasis which is not generally recognized, and which from its nature may be termed "hysterical lithiasis." This unusual demonstration of an abnormal psychologic process is manifested by symptoms simulating those of acute renal colic. In order to make the deception complete, a stone will be produced by the patient shortly after the colic, which on casual observation may be mistaken for renal calculus. Nine cases of this unusual form of hysteria have been recorded at the Mayo Clinic; eight of these patients were women. All gave a history of having passed urinary calculi repeatedly; one patient claimed to have passed more than 200 stones. Examination of the specimens invariably showed the presence of inorganic material, which made the diagnosis of foreign body certain. Three of the patients were morphine addicts.