Tea is one of the most popular beverages in many countries and is the second, after the pure water, most consumed drink in the world, but consumption habit varies between different countries. Incidence of different diseases varies widely across the world and many investigators relate these differences to diet including habitual tea drinking. It is consumed mostly as green tea and black tea where other forms such oolong; red or white teas are less popular. Green tea was extensively investigated on its health benefits but black tea is only now catching the serious attention of scientific community. Compounds contained in black tea such as theaflavins and thearubigens contribute to black tea dark color and distinctive flavor. They also provide health benefits originally attributed solely to green tea. This review summarizes available information on bioactive ingredients of tea, their bioactivity and relation to diseases, bioavailability with special attention to health benefits of black tea.