Four bacteria capable of degrading certain components of crude oil were examined with respect to their degradation abilities. Acinetobacter sp. T4 and Rhodococcus sp. PR4 could degrade various alkanes, while Pseudomonas putida PB4 was able to degrade benzene and alkylbenzenes with a C-1 to C-4 Side chain. Sphingomonas sp. AJ1 has been shown to be capable of degrading naphthalene and phenanthrene. The biodegradation of Arabian light crude oil by a mixed bacterial population constituted of these four bacteria was examined. This population degraded 40% of the saturated fraction and 21% of tile aromatic fraction of the crude oil in 10 d, a degree of degradation equivalent to that attained by many microbial consortia specifically enriched for the biodegradation of crude oil. In a mixed culture of the four strains, Acinetobacter sp. T4 and P, putida PB4 grew, but the growth of the other two strains was not significant. A consortium of Acinetobacter sp, T4 and P. putida PB4 exhibited the same degree of biodegradation as that of the mixed population of the four bacteria. In this two-strain consortium, Acinetobacter sp. T4 degraded components in both the saturated and aromatic fractions, and produced metabolites that could support the growth of P. putida PB4, The latter strain grew on these metabolites, and degraded aromatic compounds present in the crude oil.