This chapter overviews volatile compounds in freshly collected milk and in different types of heated milk and their relation to flavors and off-flavors. Undesirable flavors may also be observed when certain compounds are released from the forage by the cow's metabolism. Milk fat is an important source of flavors and off-flavors in milk. Proteins and lactose can be important sources for the formation of flavor compounds in milk by chemical, enzymatic, and microbial processes. A flavor reminiscent of boiled milk or eggs, mainly caused by hydrogen sulfide, probably together with some other sulfur compounds. Defects arising during and after processing may occasionally be a serious problem in milk. Heat-induced flavors are "normal" if they are in accordance with the flavor profile of the corresponding type of milk. When milk is exposed to light, off-flavors may develop, depending on the intensity and wavelength of the light source, the translucency of the packaging material, and the duration of exposure.