A search was carried out for mutants, defective in the conversion of stearic acid to oleic acid in effort to improve the quality of lipids produced by Cryptococcus curvatus ATCC 20509. Mutants were selected as unsaturated fatty acid (Ufa) auxotrophs. After treatment of parent organism with Ethyl methanesulfonate (EMS), 11 oleate-requiring auxotrophs were isolated. Only 3 of them were real unsaturated fatty acid (Ufa) mutants, while the other 8 were designated as fatty acid synthetase (Fas) mutants. The amount of saturated fatty acid (SFA) was about 65.2% in the lipids extracted from on Ufa mutant named UfaM3 and it was significantly higher then that of the wild-type (WT) (46.6%) and similar to that of cocoa butter (60.4%).