A tetrahydrofuran-degrading bacterial strain, which had previously been tentatively assigned as Rhodococcus sp. strain 219, has now been identified as Rhodococcus ruber using physiological and chemotaxonomical tests, A comparison with the type strain DSM 43338 has revealed that the new strain differs in its ability to degrade or convert tetrahydrofuran and compounds of similar structure such as 2,5-dimethyltetrahydrofuran or tetrahydropyran. Tetrahydrofuran acts as an inducer for its degradation. When tetrahydrofuran-induced cells were incubated with 2,5-dimethyltetrahydrofuran two primary metabolites could be detected by gas chromatography, and 2-hydroxyhexane-5-one and hexane-2,5-dione were isolated and characterized by H-1-NMR spectroscopy or as dinitrophenylhydrazones. The these intermediates is consistent with hydroxylation of the cyclic ether, which has not yet been described in microorganisms.