Plants of the genus Hypericum are widely used in folk medicine for the treatment of gastric ailments, burns, inflammation, microbial infections, skin wounds and psycological disorders. Five endemic Hypericum species in Turkey (H. kotschyanum Boiss., H. scabroides Robson & Paulter, H. salsugineum Robson & Hub.-Mor, H. thymopsis Boiss. and H. uniglandulosum Hausskn. ex Bornm.) were tested in vitro for antioxidant activity. Methanol-acetone extracts of the aerial parts of H. salsugineum and H. scabroides possessed significant activity which may be attributed to their strong reducing power, DPPH and superoxide radicals scavenging, metal chelating and lipid peroxidation inhibitory activities. The superoxide radical scavenging activity of H. scabrides (EC50: 1.14 +/- 0.046 mg/ml) and H. salsugineum (EC50: 1.09 +/- 0.096 mg/ml) were more remarkable than that of other three species. The antimicrobial study was carried out by microbroth dilution technique. The extracts showed good antibacterial activity against Gram-positive bacteria but no antifungal activity. Chloroform extract of the aerial parts of FL scabroides showed antibacterial activity against Staphylococcus aureus with a MIC value of 39.06 sg/ml.