Hydrocarbon-oxidizing bacteria isolated from soil samples from different climatic zones (Belarus, Libya, Iraq, and Antarctica) were studied. Techniques of physiological, biochemical, and molecular genetic analysis were used to identify 18 strains, most of which belonged to nonmycelial actinomycetes. Informative genetic markers used for identification of bacteria of the genus Rhodococcus were the genes alkB (for R. pyridinivorans), rpoC and groES (for R. erythropolis), groEL (for R. opacus), and random chromosome fragments (for R. opacus and R. pyridinivorans). Bacteria isolated from Libyan sandy soil and Antarctic soil and identified as Dietzia sp. 10-15, Deinococcus sp. А2-6, Alkanindiges sp. A36-1, and Alkanindiges sp. A36-3 exhibited low similarity of their 16S rRNA gene sequences to those of the closely related species and differed from them in a number of physiological and biochemical characteristics, which supported their identification as members of new species. Comparative physiological, biochemical, and fingerprint analysis of the strains belonging to the same species revealed intraspecific polymorphism. Strains capable of growth at high and low temperatures, resistant to UV-irradiation, elevated NaCl concentration, and acidic or alkaline conditions were revealed. This is the first report of oil degradation by R. pyridinivorans 5Ар at elevated temperature (45°C) and by R. erythropolis A2-h2 at 4°C.