Extracts of Aspergillus fumigatus are required for the measurement of specific antibodies that are important indices in the diagnosis of allergic bronchopulmonary aspergillosis (ABPA). This study investigated the effect of different culture conditions on the production and release of antigenic and allergenic proteins of A. fumigatus. Increasing the incubation temperature from 25°C to 37°C altered the production of proteins by the mycelium which resulted in the release of a greater number of proteins that reacted with precipitating antibodies. Static sporulating cultures produced a much wider antigenic spectrum than shake cultures although the number of precipitating proteins (5 and 3 respectively) and major IgE binding proteins (5 and 3 respectively) was not greatly altered. The widest range of proteins bound by precipitating antibody or IgE from ABPA serum were released into the culture filtrate during 28 day static incubation at 37°C. The resultant extract proved useful for screening patients for specific IgE and will provide a starting material for the identification of individual antigens or allergens.