As for the treatment of mycosis, there are reported many therapeutical method using antibiotics, chemotherapeutics, vaccine or immune serum; however, there is no report on the basis of prevention of mycosis as yet. The author assumed that the situation might be caused by uncertainity on the mechanism of manifestation of the symptome and that the lung affection, that reported already on the Part Ⅰ of this thesis, was resulted from repeated and large-amounted invasion of the fungus into body. The author studied mass invasion of Aspergillus and found the specific histological change on lung following by 1 or 2 large-amounted inhalation of the fungus to mouse. Also the author observed the preventive effect of the filtrate of the broth into which Asp. oryzae was cultred and the polysaccharide prepared from prepared from pellicle of the organism in the light of the lethality and specific change on tissue. The filtrate and the polysaccharide were given to mouse subcutaneously 1-3 times before the inhalation.