To elucidate the cause of severe asthma in adults, an animal model of chronic asthma was established in guinea pig sensitized by intraperitoneal injection of Ascaris suum and inhalation of the antigen repeated ten times. Then airway hyperresponsiveness, inflammatory cells and eicosanoids in the bronchoalveolar lavage fluid (BALF) and peripheral blood were examined. Airway responsiveness was acquired after inhalation of the antigen. Two types of airway responsiveness were observed ; accerelating-group and recovering-group. Total cell count and numbers of eosinophils and neutrophils in the BALF were significantly increased in the accerelating-group compared with the recovering-group and the control-group. The TXB2 level in the BALF was increased in the accerelating-group, and the LTB4 level in the BALF and peripheral blood were also increased in the accerelating-group. These findings suggest that the airway hyperresponsiveness is caused by eicosanoids, such as thromboxanes and leukotrienes produced by some inflammatory cells which are organized by activated lymphocytes as well as mast cell-basophils.