Histamine plays an important role in bronchoconstriction mediated by histamine receptors which provoke bronchial asthma attack. In this study, we measured H1 and H2 receptors in the guinea pig lung membrane fraction and obtained the following results. The maximum binding (Bmax) of H1 receptors in the guinea pig lung membrane fraction was significantly higher in the OA-sensitized group than that in the non-sensitized group, but affinity (Kd) did not differ between the groups. Otherwise, the maximum binding (Bmax) of H2 receptors in the guinea pig lung membrane fraction was significantly lower in the OA-sensitized group than that in the non-sensitized group. But affinity (Kd) did not differ between the groups. These findings suggest a close association of Histamine receptors both H1 and H2 in the pathology of asthma.