The phospholipid composition of Schizosaccharomyces pombe was not markedly affected by changes in the phosphate concentration of the medium or phase of growth. The major fatty acids in the total lipid extract and purified phosphatidylinositol were palmitic acid and oleic acid. Phosphatidic acid was synthesized by acylation of l-3-glycerophosphate in Schiz. pombe and phosphatidate phosphohydrolase was present. Phosphatidylinositol synthesis from inositol occurred in the absence of CDP-diglyceride. Even with dialysed cell-free preparations, the inositol lipid was synthesized by an apparently energy-independent route, at rates greater than would be required during cell growth. Phosphatidylinositol appeared to be broken down by a phospholipase D. All the enzymes examined were particulate; similar activities were found in Saccharomyces cerevisiae.