Incorporation of [1-14C]palmitic acid into neutral lipids and phospholipids of rat cerebral cortex was examined in vitro in normal Krebs--Ringer bicarbonate buffer containing 3% (wt/vol) albumin and 0.75 mM palmitic acid. Under standard assay conditions, radioactivity in the triacylglycerol fraction increased rapidly during the first 30 min, and then decreased after 60 min, with corresponding increase in radioactivity in phosphatidyl choline, phosphatidyl ethanolamine, and a fraction of phosphatidyl inositol plus phosphatidyl serine. Diacylglycerol was shown to be an intermediate metabolite. Radioactivity increased in triacylglycerol, and decreased in phosphatidyl choline and phosphatidyl ethanolamine throughout incubation under N2 gas. In the fraction of phosphatidyl inositol plus phosphatidyl serine, radioactivity decreased after 30 min during incubation under N2 gas. A possible acylation--deacylation cycle, in which triacylglycerol could be a source of free fatty acids for phospholipids, is discussed.