A 50-year-old Vietnamese man suffered recurrent episodes of hypokalemic periodic paralysis during treatment for thyrotoxicosis. Suspected precipitants of the paralysis were oral prednisolone, strenuous exertion and poor compliance with medications. Propranolol prevented the periodic paralysis. Control of the thyrotoxicosis was complicated by a florid skin reaction attributed to carbimazole, and was ultimately achieved using radioiodine.