An immunopharmacological profile of 2, 7-dimethyl-3-nitro-4H pyrido [1,2-a] pyrimidine-4-one (P-I) has been investigated using in vitro and in vivo models representing various features of Type I allergy. P-I prevented compound 48/80-mediated histamine release from rat peritoneal mast cells. A promising anti-inflammatory activity of P-I was evident in active paw anaphylaxis (mice) and carragenan-induced paw edema (rat). P-I inhibited eosonophil accumulation and eosinophil peroxidase activity in bronchoalveolar lavage fluid from ovalbumin challenged balb/c mice: in these animals blood levels of IL-5, and CD4+ T cells also remained attenuated. A promising bronchorelaxant effect of P-I was observed in histamine-contracted guinea pig tracheal chain via its antagonism to H1 receptor. These findings were compared with some known compounds (ketotifen, cetirizine and promethazine). The anti-histaminic, anti-inflammatory and bronchorelaxant activities of P-I has been discussed in context with its potential profile as an anti-allergic and anti-asthmatic agent.