The cardiac effects of PAF antagonist Ginkgolide B(BN 52051) have been investigated on the isolated perfused guinea pig hearts maintained at the constant hydrostatic perfusion pressure of 80 cm water. PDE(Phosphodiesterase) inhibitor KR-30289 was used as a positive control to see the positive inotropic effects on the perfused hearts. In this expriments, Ginkgolide $B(10^{-5}-SM)$ showed negative inotropic effects by decreasing of LVP, LVDP, LV dp/dt, HR and RPP(Rate Pressure Product). Ginkgolide B also decreased the number of extrasystole by $51.9\%(from;23.75pm9.22/min;to;11.43pm435/min)$ induced by global ischemia and reperfusion. The rate, [-dp/dt]/[+dp/dt] increased in preischemia but decreased in postischemia. 1n the separated study the injection of 1ml of Ginkgolide B$(10^{-4M})$ on the isolated heart, increased coronary flow(CF) by $11.8\%(from;7.5pm7.65ml/min;to;8.5pm0.29ml/min)$ and decreased the number of extrasystole by $47.6\%(from;21pm5.92/min;to;11pm5.27/min)$. In conclusion, Ginkgolide B showed antiarrhythmic and protective effects by decreasing the number of extrasystole and by increasing the coronary flow, respectively.