Ruthenium(III) catalysed oxidation of 1-phenylethanol and substituted 1-phenylethanols by phenyliodosoacetate (pia) in acetic acid is studied and a probable mechanism suggested. The proposed mechanism involves the formation of a complex of Ru(III) and (pia) which reacts with the substrate, S, in a slow step. Spectrophotometric evidence for this complex is presented. Studies on the effect of substituents suggest a transition state involving a π-complex. © 1985 Indian Academy of Sciences.