ABSTRACT In France and other European countries, natural thermal spring waters have been used for centuries to treat countless patients. Because of the methods and conditions of cure advocated for these waters, they had never until recently been seriously considered as a drug. However, extensive work carried out in French spas has provided scientific evidence in support of the therapeutic usefulness of spa treatment. This review presents the evidence in favour of aerosol treatment of broncho-pulmonary conditions with thermal water in certain spas. It successively discusses the historical background of these waters, their physical, chemical and bacteriological properties, their mode of administration, their pharmacological activity on isolated organs, whole animals and enzymes, their pharmacokinetics after administration to animals and man, their clinical pharmacology in animals and man and finally their clinical activity. Despite the inescapable difficulties encountered in evaluating spa treatment, the mo...