Current research into free radicals has confirmed that plants rich in antioxidants play an essential role in the prevention of many diseases. The potential antioxidant activities of Pterocarya fraxinifolia bark and leaves investigated employing six in vitro assay systems. IC50 for DPPH radical-scavenging activities were 3.89 +/- 0.09 for leaves and 41.57 +/- 1.30 microg mL(-1) for bark, respectively. The leaf extract exhibited a good reducing power at 2.5 and 80 microg mL(-1) that was comparable with Vit C (p>> 0.05). The extracts also showed weak nitric oxide-scavenging activity and Fe2+ chelating ability. The peroxidation inhibition of extracts exhibited values from 92 to 93% at 72nd h, almost at the same pattern of Vitamin C activity (p>> 0.05). Based on higher total phenol and flavonoid contents in leaves, higher antioxidant activities were observed in leaf extract. In addition, chemical composition of leaf essential oil was determined. The major compound was bisabolol oxide A (23.6%). Sesquiterpenes and monoterpenes are the major compounds in leaves essential oil. Presence of these compounds may be a reason for the good antioxidant activity of leaf extract.