As most of the fungi pathogenic for man are always demonstrable in the natural world, it can not make a diagnosis of mycosis to find a fungus in the secretion or in the excrete of the patient by mycological examinations. Also histological examination is so unpractical because of uneasiness especially in the case of deep mycosis. Thus there are remained only immunological and serological reactions in the diagnosis, still there is not so widely accepted method specific for candidiasis, histopoasmosis or cryptcoccosis. The author observed a lung affection which occured among the emplyees of a chick food factory in Kagawa prefecture in higt prevalence between 1957 and Jum. 1958, and examined all employees in mycological and serological method. The author also studied hemoaggulutination reaction using the erythrocytes sensitized by Asp. oryzae, Asp. fumigatus and a fungous strain isolated from a patient (Takabata Strain) with the serum of employees or of rabbit kept in the factory or inoculated with Asp. oryzae. Observing the higt specificity among the reaction mentioned here, the author supposed this lung affection as lung aspergillosis caused by Asp. flavus-oryzae group.