An examination of 213 male psoriasis patients showed neither a positive nor a negative influence on the skin lesions for 87,9% of the patients, an improvement for 10,7% and a deterioration for 1,4% in a sauna bath. Evaporation measurements of untreated psoriasis in a sauna bath showed a 50% decrease in perspiration. This was proved also by the silicone print method. These values increased after removal of the psoriasis-scales. Skin temperature measured at the same time did not show any difference.