The invention provides polypeptides and encoding nucleic acids of aldehyde dehydrogenase variants. The invention also provides cells expressing aldehyde dehydrogenase variants. The invention further provides methods for producing 3-hydroxybutyraldehyde (3-HBal) and/or 1,3-butanediol (1,3-BDO), or an ester or amide thereof, comprising culturing cells expressing an aldehyde dehydrogenase variant or using lysates of such cells. The invention additional provides methods for producing 4-hydroxybutyraldehyde (4-HBal) and/or 1,4-butanediol (1,4-BDO), or an ester or amide thereof, comprising culturing cells expressing an aldehyde dehydrogenase variant or using lysates of such cells.