Tetracycline is a potent broad spectrum antibiotic that has played a pivotal role in human and animal health for over 60 years. Tetracycline is a linear tetracycle which can be degraded under various conditions, such as acidity, alkalinity, heat, oxidation, light and temperature. The degradation products are not biologically inert; rather, they are oxidative and isomeric analogues with unique physical and chemical properties that are not well characterised. The Tetracycline Degradation Set provides the major degradation products described in the literature as a tool for understanding and monitoring the fate of tetracycline on storage and in biological systems.