Nonproliferating cells of Mycobacterium vaccae that were grown on propane could mineralize limited amounts of trichloroethylene. Intermediates in the biodegradation of trichloroethylene were 2,2,2-trichloroethanol and 2,2,2-trichloroacetaldehyde. Trichloroethanol was completely degraded when added to a nonproliferating cell suspension of Mycobacterium vaccae. Addition of toluene to the reaction mixtures effected a 50% increase in the mineralization of [14C]trichloroethylene.