With the purpose of measuring the frequency of allergies of the respiratory tract to airborne fungi in São Paulo, Brazil, 201 patients with bronchial asthma and/or allergic rhinitis were submitted to intradermal testings with allergenic extracts of 42 fungus genera isolated from the air in São Paulo. The extracts of these fungi were prepared according to Coca's method and then standardized by the weight by the volume method. At first, the patients were submitted to intradermal testing with the total polyvalent (TP) extract, getting positive reaction in 70 of them (34.8%). The patients with positive reaction to the TP were tested with the 42 individual extracts and 74.3% of them reacted positively to one or more extracts. These results led us to the conclusion that the most frequent fungi in the air of São Paulo were not the ones which cause the highest number of positive intradermal reactions. Therefore, the convenience in employing as many allergens as possible in intradermal testings for diagnosis should be reinforced.