Thyrotoxic Periodic Paralysis (TPP) is a rare complication of thyrotoxicosis and is up to 20 times more common in males. Cases usually present with painless muscle weakness precipitated by heavy exercise, fasting, an alcohol binge or large carbohydrate meal. Serum potassium is low in the majority, but normokalaemic (or even hyperkalaemic) TPP is recognised. Acute treatment of any electrolyte disorder, administration of a beta-blocker and treatment of the thyrotoxicosis leads to complete resolution. This rare diagnosis should be considered by the Acute Physician when confronted with any case of muscle weakness.