Methods for the preparation of 3,4-dihydroxyphenylacetaldehyde, 4-hydroxy-3-methoxyphenylacetaldehyde, and 3,4-dihydroxyphenylglycolaldehyde are described. Michaelis constants and maximal velocities for the reduction of a number of biologically important aldehydes by horse liver alcohol dehydrogenase and NADH are tabulated.