The biodegradation of the heavy fraction of the raw petroleum from Cusiana by Pleurotus ostreatus fungi was studied, specially emphasizing on the study of the cultivation without additional vegetable oil in the substrate, which was have been used in other cases like stimulant in the process, the concrete case of the biodegradation was also proved in soil. The work was developed in three phases: biodegradation of raw petroleum on lignocelulosic substrate without adding vegetable oil; study of inhibition of growth of the fungi in presence of its main competitor Trichoderma spp and at different concentrations of inhibition substances; and finally, biodegradation of raw petroleum in loam. From the obtained results, it is concluded that: It is possible to degrade raw petroleum without adding vegetable oil. The required optimal time for the biodegradation in lignocelulosic substrate is near to 45 days for an optimal raw petroleum concentration of 10.52%. The inhibitor that favours the Pleurotus growth in presence of its main competitor is the Mertect®, in concentration of 20 mg/kg. It is possible a raw petroleum biodegradation nearto70% in loam, under simulated field conditions