SUMMARY: The early stages in the oxidation of naphthalene by five micro-organisms were investigated. In all the organisms. d-trans-1:2-dihydro-1:2-dihydroxy-naphthalene. salicylic acid and catechol appeared to be intermediate oxidation products. Washed cells grown on naphthalene oxidized α- and β-naphthol, but whether these compounds are true intermediates remains undecided.