The Clark oxygen electrode was used to measure the microbial oxidation of hydrocarbons using preparations of resting cell suspensions. A strain of Corynebacterium sp. (7E1C) which utilized n-octane as sole carbon and energy source was examined for its ability to oxidize a variety of hydrocarbon substrates. The oxidation by resting cells exhibited an optimal temperature of 30° and an optimal pH range of 7.0-7.6. 1-Octanol, octanal, and octanoic acid were oxidized at rates comparable to n-octane. With the exception of n-decane, n-alkanes from pentane through heptadecane were attacked with a progressive increase in specific activity up the homologous series to n-octane, followed by a decrease as the hydrocarbon chain became progressively longer. n-Alkenes and halogenated n-alkanes substituted in the one position were oxidized at appreciably lower rates than the corresponding n-alkanes. Iso-Alkanes, cyclo-alkanes and aromatic hydrocarbons were relatively unsusceptible to oxidative attack. © 1969 Springer-Verlag.