A quantitative and qualitative study of the atmospheric fungi in a big silo was carried out over a period of one year (April 1973--April 1974). About 6 to 12 Petri dishes with Czapek medium were exposed for 5 minutes every month at different floors of the silo. The study showed:--a very high number of fungi colonies, reaching as many as 903 in March 1974 (a total of 60 min exposure); the dominant fungus was penicillium which was, however, overpassed in certain months by aspergillus (flavus and fumigatus) which in May 1973 reached about twice the incidence of penicillium. Cladosporium-hormodendron, the dominant fungus in our country, ranked third on the list, about the same as rhizopus nigricans and much before alternaria (less than 30 colonies per 60 min Aspergillus niger, actinomicetes, yeasts, etc. were found in an even lesser amount. It is assumed that the dominant fungi may play a part in the etiopathogeny of the bronchial asthma of workers in such silos but investigations should be furthered before reaching a final conclusion.