Tetany is a series of symptoms characterized by painful muscle cramp that derives from enhanced neuromuscular excitability due to hypocalcemia, hypomagnesemia or alkalosis. In a broad sense, tetany includes associated sensory disturbance. Typical symptoms of tetany include carpopedal spasm, laryngospasm and generalized seizure. Chvostek and Trousseau signs are provocative tests for diagnosis of latent tetany. Many diseases including endocrine disorders like hypoparathyroidism and alkalosis by hyperventilation can cause tetany. Infusion of calcium or magnesium is effective as an acute therapy for tetany. However, subsequent diagnosis and treatment of underlining diseases are mandatory.