Quinones are redox-active molecules containing a cyclohexadienedione ring and exist either as ortho or para isomers depending on the location of the ketone centers in the ring. Quinones are commonly used as oxidants in chemical reactions and as enzymatic cofactors in biological processes including photosynthesis and cellular respiration, as well as in several important anticancer antibiotics such as mitomycin C, daunomycin and doxorubicin. The susceptibility these structures have towards reduction to quinols and semiquinone radical intermediates is influenced by electronic effects of substituents. This review discusses the reduction chemistry of quinones and its relevance to the biological and pharmaceutical properties of important quinone antibiotics.