Conditions for the culture of Pleurotus spp. mycelium using rancid frying oils were investigated. Among the six strains tested, Pleurotus ostreatus CBS 03 showed the greatest mycelial growth on fish paste and ramyon frying oil, and was used in this study. The optimum temperature and pH for mycelial growth were from 25 to $30^{circ}C$ and pH 5.5 to 6.0, respectively. Tryptone for mycelial growth was better than any other nitrogen sources. The addition of $KH_2PO_4 and MgSO_4$ enhanced mycelial growth at 0.2 and 0.01% on fish frying oil, and at 0.1 and 0.03% on ramyon frying oil. Among the vitamins used, thiamine and nicotinic acid were the most effective ones.