The objective of the study was to test the effects of inhalation crenotherapy using the radioactive, fluoridated oligomineral waters from the Merano Spa on both subjects with specific upper respiratory tract phlogosis and normal subjects. The double-blind study was performed on a population of 27 adults of both sexes treated with radioactive-fluoridated water (group A) and 20 subjects, suffering from the same chronic catarrh pathology, selected with the same criteria but treated with inhalation of steam and an aerosol using drinking water from the municipal water supply (group C). In addition, a group of 13 subjects--which in terms of age and sex were statistically comparable to groups A and C but who did not show any signs of acute or chronic upper respiratory tract pathologies (group B) were also treated with the radioactive-fluoridated waters. All subjects included in the study underwent the following tests before and after the cycle of crenotherapy: Objective E.N.T. examination. Computerized Active Anterior Rhinomanometry. Detection of the ciliary mucous transport (CMT) time. Nasal cytology. Physical and immunochemical examination of the nasal mucous. The results of this study--seen in the trend in some parameters monitored both before and after the cycle of crenotherapy using Merano Spa water--clearly show that that the crenotherapy studied had an effect on aspecific chronic phlogosis of the upper respiratory tract. In fact, among other things, group A showed decreased nasal resistance, increased nasal respiratory flow, normalized mucociliary transport, decreased bacterial flora and an increased number of plasma cells in the rhinocytogram. In addition there was an increase in the following values in the nasal mucous: Albumin, non-secretory Immunoglobulin and the secretory portion of secretory Immunoglobulin A. None of these variations are seen in the results from the control group treated with municipal drinking water. After treatment with Merano spa water, the pathology-free subjects showed variations in the parameters in line with those found for group A. This biological reality can most likely be attributed to the favorable response of the respiratory mucosa, promoting anti-infection defenses.