Aldehydes are highly reactive molecules. A lot of enzyme systems participate in the metabolism of aldehydes, and one of the most important enzyme systems is aldehydes dehydrogenase (ALDH) superfamily, which is composed of NAD (P) ⁺-dependent enzymes that catalyze aldehyde oxidation. This paper presents a review of what is currently known about each member of human ALDH superfamily, including the pathophysiological significance of these enzymes, in hopes of providing information for future studies on comparison of roles among ALDH members and roles of ALDH superfamily in development of cancers.