The effects of ginkgolides(natural mixture of ginkgolides, ginkgolide B, ginkgolide C) and flavonoids(quercetin, kaempferol, myricetin), extracted from Ginkgo biloba, on ADP and PAF-induced platelet aggregation in vitro and ex vivo were investigated. In these experiments, both of ginkgolides and ginkgoflavonoids did not affect the ADP(5 $mu{M}$) induced platelet aggregation in vitro. The IC$_{50}$ value on PAF (0.3 $mu{M}$) induced platelet aggregation were 2.52 $mu{M}$ (ginkgolide B) and 6.35 $mu{M}$ (natural mixture of ginkgolides) and 2.80 $mu{M}$ (mixture of ginkgolide B and quercetin). Oral administration of ginkgolide B (1 and 3 mg/kg) and quercetin (3 and 9 mg/kg) to rabbits inhibited ex vivo PAF induced platelet aggregation in a dose-dependent manner. Ginkomin-F tablets administered to the diabetic patients showed inhibitory activities on the ADP and PAF induced platelet aggregation in a dose and time dependent manner.