To clarify the mechanism of intractable asthma, we examined the cellular content and chemical mediators in BALF and peripheral blood of a chronic asthma model which we had already established by inhalation of ascaris suum antigen. The serum levels of antigen specific IgG antibody on the eighth day were signicantly higher than those before inhalation. The serum levels of antigen specific IgG(1) antibody increased on the eighth day compared with levels before inhalation. The serum levels of antigen specific IgG(2) antibody as a blocking antibody increased and immediat asthmatic response (IAR) gradually improved until the fourth day. The number of eosinophils after eight days of inhalation was decrease in peripheral blood but was significantly increased in BAL and lung tissue. The serum levels of LTC(4) after eight days of inhalation decreased significanlty compared to those after one day of inhalation. LTB4 concentration in BAL after eight days of inhalation were significanlty lower than those after one day of inhalation. Histamine concentrations were increased in BAL in both the IAR and dual asthmatic response (DAR) animal model. These data suggest that intractable asthma was induced by many kinds of chemical mediators produced by inflammatory cells including eosinophils, mast cell-basophils, neutrophils and lymphocytes.