A number of aromatic aldehydes have been reacted with catalytic amount of KCN in boiling DMSO. Benzaldehyde (1a), 2-nitro-, 3-methoxy-, 2,6-dichloro- and 2,3,4-trimethoxybenzaldehydes (1b-1e) and α-naphthaldehyde (1f) gave corresponding benzonins (2a-2f). 3-Bromo- and 2-chlorobenzaldehydes (3-a-3b) changed to benzils (4a-4b) where as 4-bromo-, 3-chloro-, 4-methoxy-, 4-nitro-, and 3,5-dimethoxybenzaldehydes (5a-4b-5b) and β-naphthaldehyde (5f) underwent oxidation to acids.(6a-6f)