BACKGROUND: Allergic disease is an inflammatory disease, whose main inflammatory cells are eosinophils, mast cells, and T lymphocytes. From that point, new therapeutic targets on allergic inflammation focusing on them are under investigation. We extracted four isoflavonoids from Sophorica japonica such as sophi, orobol, genistin, and genistein which has been known as PTK antagonist. We documented those three iso-flavonoids except genistein had an anti-inflammatory effect as potent as dexamethasone on carageen-induced ear model. Also they had antagonism on the Y-16 cell line, whose growth is dependent on IL-5. OBJECTIVES: From above results, in this experiment, we tried to find antagonistic effects of those compounds on IL-5 using the inhibition of eosinophil activation and survival in vitro and possibility of anti-allergic medicine. METHODS: LTC4 by RIA and ECP for degranulation by UniCAP(TM), which had been used previously were activation markers. RESULTS: Among those compounds, sophi was the most potent antagonist on IL-5 induced LTC4 release, degranulation, and survival. Orobol and genistin also had antagonism on them, but genistein, an antagonist of PTK didn't show any antagonistic effects. CONCLUSION: From these results, we concluded those three iso-flavonoids were IL-5 antagonist, and the mechanism of it might not be through PTK signaling.