Antioxidants are important species which possess the ability to protect the body from damage caused by free radical-induced oxidative stress. A variety of free radical-scavenging antioxidants exist within the body many of which are derived from dietary sources. There is currently much interest in the antioxidant role of flavonoids and other polyphenols found in tea, wine, fruit and vegetables. Enhanced chemiluminescence is a simple technique which can be used as a rapid and sensitive assay for measuring the antioxidant activity of beverages such as green and black tea. This article examines the impact of water temperature, stewing time, leaf concentration and the addition of milk upon the antioxidant activity of black tea solutions. The antioxidant activity of a range of commercially available black and green teas has also been measured.