This chapter provides information on the off-flavors that are arranged by type of food product. It discusses some off-flavors that can be found in a wide range of products and highlights the negative aspects. Packaging materials can be the cause of off-flavors in several ways. Among the off-flavors caused by contamination, the most frequently occurring are those deriving from chlorophenols and chloroanisoles. The dominant off-flavor in water and the water environment can be described as musty/earthy. Besides geosmin and methylisoborneol, blue-green algae can produce other volatile compounds that contribute to aquatic taste and odor problems in water; a review of these compounds is given by Slater and Blok. Besides the fact that petroleum compounds cause off-flavors, some petroleum components are also harmful to animals and plants.