In order to clarify the pathophysiological role of the chemical mediators, the releases of kinins, histamine and leukotriene C4(LTC4) into the nasal cavity were measured following nasal allergic challenge in ovalbumin(OA)-sensitized guinea pigs, or following nasal stimulation with one of these chemical mediators in OA-non-sensitized animals. In sensitized animals, an increased vascular permeability of nasal mucosa was recognized immediately after antigenic stimulation and lasted for 60-90 minutes. Releases of kinins and LTC4 into the nasal lavage fluid augmented not only immediately after the antigenic challenge, but also during 60 to 90 minutes after the stimulation. Release of histamine into the nasal lavage fluid was observed only immediately after the antigenic stimulation. In non-sensitized guinea pigs, nasal stimulation with bradykinin accelerated nasal vascular permeability. Nasal stimulation with histamine or LTC4 resulted in increase of nasal vascular permeability and of kinins concentration in the nasal lavage fluid. These results suggest that kinins might be concerned with the immediate and later vascular permeability during the allergic response.