By supplying styrene in the gas phase as the sole carbon and energy source, styrene-degrading aerobic microorganisms were readily isolated from soil samples. They were identified as Corynebacterium pseudodiphtheriticum and similar species, or Pseudomonas sp. Growth experiments on some aromatic compounds, resting-cell reactions with them, and the measurement of degrading enzyme activities suggest that Corynebacterium sp. AC-5 and St-5 strains metabolize styrene through styrene oxidation into styrene oxide, then convert it into phenylacetaldehyde by a reaction using styrene oxide isomerase, and phenylacetaldehyde is reduced to 2-phenylethanol. The Corynebacterium sp. ST-10 strain did not have styrene oxide isomerase, and metabolized styrene oxide by an unknown enzymatic reaction. Possible metabolism of styrene was proposed for the Corynebacterium strains.