The fatty acids of a temperature-sensitive mutant of Saccharomyces cerevisiae defective in cell division and respiration were compared with those of its wild-type strain. The lipids were solvent-extracted from stationary phase cells grown in glucose complete medium. Cells were grown at 23°, 30°, and 37°. The fatty acids were transmethylated and analyzed by programmed gas-liquid chromatography. The major fatty acids of both mutant and wild-type cells were palmitic (16:0), palmitoleic (16:1), stearic (18:0), and oleic (18:1). The data indicate that the mutant had an altered concentration of these fatty acids. Also, the concentration of unsaturated fatty acids in the mutant increased as the temperature was raised from 30° to 37° while the concentration of unsaturated fatty acids in wild-type cells decreased over the same temperature span.