The phenolic profile and antioxidant activities of oolong tea extract were investigated after tea was steeped in 90 or 100 degrees C water for 3 or 10 min. The extraction yield increased with increasing temperature and extended steeping time. However, higher temperature and longer time (100 degrees C water for 10 min) led to loss of phenolics. The aqueous extract of oolong tea (AEOT) at 100 degrees C for 3 min exhibited the strongest antioxidant activity. The major polyphenolic components of the AEOT were identified as (-)- epigallocatechin (EGC), (-)- epigallocatechin gallate (EGCG) and (-)-epicatechin-3-gallate (ECG). The two major catechins (EGC and EGCG) in the tea infusion contributed significantly to the investigated antioxidant activities [i.e., the 2,2-diphenyl-2-picrylhydrazyl hydrate (DPPH) radical scavenging and superoxide radical scavenging activities] with high correlation values in r = 0.9486 and 0.9327 for the EGC and r = 0.9592 and 0.8718 for the EGCG, respectively.