X-ray surface therapy in the treatment of skin diseases has grown to occupy a very important, if not indispensable, place, since it was applied for the first time by Freund in 1896. The list of dermatoses for which x-irradiation in the past and also in the present is considered useful, is an extremely lengthy one. It must be said, however, that the indication to apply x-ray therapy or not, occasionally is considered from differing points of view. Variations are also encountered in the method of irradiation in those dermatoses in which otherwise agreement is reached as to the positive indication for irradiation. All this is not surprising when we remember that in dermatology the indication, as well as the irradiation methods, as a rule, is derived from empirical findings. Especially concerning the quality of x-rays to be used, the therapeutists appear to adhere to very different