The results achieved by the cultivation of the yeast Candida lipolytica on gas oil are referred. By using a distillation fraction of gas oil distilling between 180-4OO0C, containing 10-2070 of n-alkanes, the optimal condition for biomass production and deparaffination were estimated for various dilution rates and various amounts of gas oil in the medium. The main factor, which influences the yield coefficient by hydrocarbon fermentation is the polyauxie of the hydrocarbon substrate. The penetration of dispersed hydrocarbons into the yeast cell is demonstrated on electron micrographs and the velocity and reversibility of this process is estimated by using tritium-traced hexadecane.