A model of allergic bronchopulmonary aspergillosis was developed by exposing BALB/c mice to Aspergillus fumigatus (AF) Ag. Animals immunized intranasally (i.n.) with soluble AF Ag produced low levels of serum IgE compared to animals given alum precipitated AF Ag i.p. The latter treatment also produced higher levels of serum IgG1 and AF-specific IgG1 than soluble AF given i.p. or i.n.. Blood and lung eosinophilia was detected in mice repeatedly exposed to AF by i.n. but not in the groups injected i.p. Particulate AF Ag-induced striking blood and lung eosinophilia and elevated levels of serum IgE in mice preexposed to AF Ag. The results indicate that route of inoculation and physical nature of Ag determine the immune response and can be manipulated to obtain enhanced IgE, eosinophils, or both in the animal model.