Recently, many genes involved in the formation of unsaturated and polyunsaturated fatty acids (PUFAs) were isolated. In most cases, their activities were confirmed by expressing them in the well-studied model organism Saccharomyces cerevisiae because its fatty acid compositions are very simple and it does not contain PUFAs. Taking advantage of its genetic tractability and increasing wealth of accessible data, many groups are attempting to produce various useful fatty acids in the model yeasts, mainly in S. cerevisiae. This review describes typical such examples including a very recent study on the expression of a fatty acid hydroxylase gene in fission yeast Schizosaccharomyces pombe. Furthermore, the impact of the genetically engineered alteration of fatty acid composition on the stress tolerance is presented because unsaturated fatty acids have crucial roles in membrane fluidity and signaling processes. Lastly, recent attempts at increasing lipid content in S. cerevisiae are discussed.