The present authors observed and treated a siblings case of normocalcemic tetany, which is considered as belonging to Bartter's syndrome. As far as we know, there are a number of familial cases of tetany in literature, but none of them spreads over more than two generations, so that the tetany appears to be recessive in hereditary characters including our patients. Both of them presented tetanic seizures in the course of Bartter's syndrome and they were regarded as one of various manifestations of the syndrome. In other words, the Bartter's syndrome or the hypopotassemia should be one of the fundamental disorders for developing tetanic symptom. The tetanic symptoms became extinct during the treatment with spironolactone against hypopotassemia. Of the two patients, younger sister had shown an agitated depression developed on her childish and over-sensitive personality, but the depression was improved in parallel to the recovery from tetany and hypopotassemia. Therefore, it appears to be certain that the patients would have some premorbid deviation of personality traits, where symptomatic psychoses could be attributed, in the case of Bartter's syndrome. Generally speaking the psychic disorders, such as personality deviation and psychotic episode, seem to by very important symptoms in patient with Bartter's syndrome as well as in patient with hypocalcemia or hypoparathyroidism.