The assimilation of 1-14C-octadecane by the (-) 4 strain of Blakeslea trispora was studied, i.e. the kinetics of 14CO2 evolution and the distribution of the label in the biomass, proteins, lipids, and water-soluble products of the fungus. B1. trispora oxidized octadecane even in the presence of glucose in the medium. The distribution of the label between the protein and lipid fractions was different when the fungus was grown on octadecane or on a mixture of octadecane with glucose. After 6 hours of the incubation the content of the label in proteins (the experiment with 1-14C-octadecane as a carbon source) was 33 percent, and 60 percent in lipids. In the experiment with a mixture of glucose and hydrocarbon, the content of the label was 8 percent in proteins and 95 percent in lipids. These results show the participation of n-alkane and the products of its oxidation in the metabolism of Blakeslea trispora.