Our study took place in the region of the Copahue Volcano in the Andes Mountain range, 1900 m above sea level. Fifty-five patients who came to the Copahue Thermal Basin Complex (Neuquén, Argentina) for treatment of psoriasis vulgaris were clinically evaluated for participation in this study. Thermal products—waters, mud, and/or algae—were the only therapeutic agents used, except for bland emollients for xerosis. Treatment for brief periods (10 ± 3 days) resulted in notable improvement.