Two hundred patients with bronchial asthma were examined, 110 being examined during the warm and 90 during the cold months of the year. The bioclimatic constants of Sandanski resort have a favourable effect upon the clinical and functional indices. Especially manifested in the effect during the cold months of the year. The results obtained are with a high statistical significance. The very favourable effect on the bronchial asthma patients, both during the warm and cold months at Sandanski resort, makes it unique for a round-year climate treatment. The problem treats national and international interests.