The oleaginous fungus Pythium ultimum was cultivated on various solid substrates in order to achieve fungal oil enriched in the polyunsaturated fatty acids arachidonic acid and eicosapentaenoic acid. Cultivation parameters, such as incubation temperature and time, substrate composition, and moisture were optimized, so as to obtain as much as 3.5 mg eicosapentaenoic acid and 1.6 mg arachidonic acid/g of wet substrate consisting of 28.5% pearled barley, 5.75% spent malt grains, 5.75% linseed oil, and 60%; nutrient solution. (C) 2000 Elsevier Science Inc. All rights reserved.