The blood level of Vitamin B(1) in 80 cases of various dermatologic disorders was defermined with thiochrome method using permutit and considering the value of the healthy individuals and the results of other investigators, the minimum limit was established on 6.0γ% and the following results were obtained: 1) In 17 cases of healthy individuals, the average of the blood level of total Vit. B(1) was 8.34γ%, and it presented lower value in summer rather compared with in autumm. The average of the blood level of Vit. B(1) in dermatologic disorders was 6.51γ%, i.e., 1.83γ% lower than in the healthy individuals. 2) Concerning eczema acutum, it showed normal value in erythematous and desquamatous stadium. but in the rest of the stadium most of them showed lower value, in eczema chronicum it also showed lower value in cases in which the course was prolonged. 3) In dermatitis acuta and Duhring's dermatitis, the blood level of Vit. B(1) decreased in cases in which excessive exsudation could be seen, pemphigus, Domian enanthem and pellagra showed obvious deficiency of Vit. B(1). Moreover, in most of the cases of erythematodes and psoriasis vulgaris showed Vit. B(1) deficiency, but in acne vulgaris, alopecia arezta, chloasma and erythema induratum Bazin showed normal value. 4) Vit. B(1) takes part in the metabolism with close relation with the functions of many organs, as well as with other Vitamins and endocrine system; so the variation of the blood level of Vit. B(1) might not be attributed as the only cause of the previous diseases, but it could be concluded that in some of the cases, the deficiency of Vit. B(1) takes an important roll in the cause or degeneration of dermatologic diseases.