Hyperkalemia is one of the few potentially lethal electrolyte disturbances. Prompt recognition and treatment of severe hyperkalemia are expected to save lives. Electrocardiographic manifestations of hyperkalemia vary from the classic sine-wave rhythm, which occurs in severe hyperkalemia, to nonspecific repolarization abnormalities seen with mild elevations of serum potassium. We present a case of hyperkalemia and review of causes of hyperkalemia is presented, examining the electrophysiological and electrocardiographic changes that occur as serum potassium levels increase.