Experiments were carried out to evaluate the impact of the addition of ripe compost on the degradation of two C-14-labeled hydrocarbon model compounds (anthracene and hexadecane) in soil. The addition of mature compost (20% dry wt./dry wt.) stimulated significantly the disappearance of the extractable fraction of both compounds. With compost, 23% of the labeled anthracene was transformed into (CO2)-C-14 and 42% was fixed to the soil matrix irreversibly. In the unsupplemented control reactor more than 88% of the original anthracene could be recovered by either of two applied organic extraction procedures. The formation of non-extractable bound residues was less significant with [C-14] hexadecane since only 21% of the labeled carbon had become non-extractable after 103 days. The results presented show that compost could stimulate the depletion of hydrocarbons by either mineralization or the formation of unextractable bound residues (humification). The latter process might be a significant route of depletion in soil especially, for those hydrocarbons that are mineralized only slowly. The meaning of this finding for the assessment of soil bioremediation is discussed.