AbstractAlthough for centuries balneotherapy has been popular in Europe, it has not attained wide acceptance in the United States. This article is an interesting sidelight on a specific means of inducing therapeutic vasodilatation. In Covasna, Rumania, post‐volcanic CO2 gas emanations are used in the form of mofette therapy (twice daily) and CO2 waterbaths (about once daily) for the treatment of rheumatic diseases.This study concerns 40 male geriatric patients with arteriosclerosis obliterans, whose symptoms improved markedly during treatment. In each, the state of the circulation in the big toe of an affected foot was evaluated by means of radioactivity measurements after injection of I131—both before and after therapy. The results indicated that the arterial blood supply to the feet was definitely enhanced after CO2 therapy, thus promoting the formation of collateral circulation.