To detect allergic bronchial asthma to Dermatophagoides pteronyssinus and its frequency in a group of asthmatics, a study was carried out in 800 asthmatic patients and 345 healthy subjects from seven different areas of the country. We considered only allergic bronchial asthma to Dermatophagoides pt. without taking into consideration other allergens. Patients with chronic bronchopathy were not included in the study. The average frequency of disease in the group investigated was of 32 per cent. Considering the high frequency of this form of allergic bronchial asthma, specialists should grant a special attention to the early detection and treatment of this disease.