The frequency of some allergens involved in allergic bronchial asthma was studied in a group of 1177 patients who came for medical investigations to the Department of Allergy of the "N. Gh. Lupu" Institute of Internal Medicine--Bucharest between January 1980 and January 1982. The group presented a slight predominance of the female sex and the age group most affected was that of young adults. Of the allergens responsible for the onset bronchial asthma attacks the most frequent in the patients studied were: house dust (56%), moulds (53%), pollens (42%) and Dermatophagoides pteronissinus (28.3%). Of the pollens the most often involved was that of grasses. Almost a quarter of the patients started an attack of bronchospasm and presented positive reaction to certain drugs (24.39%) of which the most frequently involved was aspirin (17.4%), pyramidon (15.4%), biseptol, antibiotics (the latter being often used exagerately as self medication in the attacks of allergy mistaken for "colds"). The most frequent association of allergens were moulds--Dermatophagoides pt. (21%) and moulds--Dermatophagoides pt.--house dust (19%).