A young man of 30 yrs got himself admitted in Bangabandhu Sheikh Mujib Medical University (BSMMU) Hospital, Dhaka, Bangladesh with the complaints of suddenly developed weakness in his all four limbs. He had features of hyperthyroidism and he gave the history of similar attacks of weakness in his all four limbs in the previous months. His potassium was in the lower part of the normal range and his T4 and T3 were elevated but TSH was markedly low. He was diagnosed as a case of thyrotoxic periodic paralysis on the basis of clinical and biochemical findings. After treatment with carbimazole, propranolol and potassium replacement, patient's condition improved dramatically.