Plants of the genus Hypericum are widely used in folk medicine for the treatment of gastric ailments (including pectic ulcers), burns, swelling, inflammation, anxiety, as well as for bacterial and viral infections. The aerial parts of Hypericum rumeliacum Boiss. subsp. apollinis (Boiss. & Heldr.) Robson & Strid (Guttiferae), a perennial herb growing wild in Greece, were subjected to biological and phytochemical studies. The H. rumeliacum methanol extract showed, on the DPPH test, antioxidant activity (IC(50) = 23.61 microg/mL). The antiinflammatory activity of the extract (70 mg/kg, i.p.), in the carrageenan-induced paw oedema in rat, was studied. In this experimental model an inhibition of paw oedema, significant from the first to third hour, was observed. The histological examination confirmed resolution of the inflammatory process observed in vivo. Through HPLC analysis of the H. rumeliacum methanol extract, the naphthodianthrones hypericin, pseudohypericin and some polyphenol compounds, such as chlorogenic acid, rutin and isoquercitrin, were identified and quantified. The antioxidant activity of H. rumeliacum could be chiefly related to polyphenol compounds that are well known as the main contributors to the free radical-scavenging effects. The antiinflammatory effect of the methanol extract of the aerial parts could be due to the synergic action both of hypericin and polyphenol compounds.