Thyrotoxic periodic paralysis (TPP) is associated with hypokalemia and occurs sporadically and usually in young adult males. We report ten cases with TPP ; all were males, mean onset age was 32.4 years old. The duration of attack. Varied from 10 to 18 hours. The distribution of paralysis was confined to limb muscles; more severe in proximal limbs and lower extremities. Potassium levels during acute attack correlated with the severity of paralysis and ECG changes, but not with the severity of decrease in TSH level. In all cases, administration of potassium salts was successful in treatment of acute attack. A patient had further attack in spite of euthyroid state under the treatment of thyrotoxicosis for one year. Another patient was free from paralytic attacks by chronic administration of the potassium salt and acetazolamide without treatment of thyrotoxicosis.