Thyrotoxic periodic paralysis (TPP) is a fairly common manifestation of hyperthyroidism in Asian populations, with an incidence of about 1.9% in thyrotoxic patients, but it is rarely diagnosed among Caucasians and blacks in the Western world. The diagnosis often can be made on the basis of the clinical manifestations alone. Sometimes, periodic paralysis precedes hyperthyroidism or occurs in silent hyperthyroidism. As a result, physicians may easily overlook it even when life-threatening hypokalemia is present. The pathophysiology of this disorder is still not well understood. Correction of the thyrotoxic state is the definitive treatment. Potassium supplementation, propranolol, and spironolactone may be helpful both in the acute state and in preventing attacks.