Lithium aluminum hydride is a useful and convenient reagent for the selective reduction of various polar functional groups. It is used in diethyl ether solution, less commonly in higher boiling ethers, following the conventional procedures for syntheses employing the Grignard reagents, which the hydride closely resembles in its general pattern of behavior. The reaction proceeds with extraordinary rapidity and is relatively free of side reactions. The types of organic compounds reduced by lithium aluminum hydride and the nature of the products are detailed in this chapter. Functional groups not reduced are discussed.