Both ³H-palmitic and ¹⁴C-oleic acids were simultaneously incorporated into mouse embryo lipids from the 1-cell to the blastocyst stage. Rates of incorporation of the two fatty acids into the embryo lipids increased and differed from each other significantly after 8-cell stage (P<0.05). That of palmitic acid into the polar lipid fraction was significantly higher than that of oleic acid at all corresponding cell stages, but that of palmitic acid into the neutral lipids was significantly higher than that of oleic acid at the morula and blastocyst stages (P<0.05). In the neutral lipid fraction, the radioactivity of ³H-palmitic acid distributed in triacylglycerols, monoakyldiglycerols and diacylglycerols were significantly higher than that of ¹⁴C-oleic acid at most corresponding cell stages with the exception of high monoacyldiglycerol content in ¹⁴C-oleic acid at the 2-cell stage (P<0.05). But that of ³H-palmitic acid in fatty alcohols and monoacylglycerols was significantly lower than that of ¹⁴C-oleic acid at the most corresponding cell stages (P<0.05). In the polar lipid fraction, the amounts of ³H-palmitic acid distributed in choline phosphatides, ethanolamine phosphatides and sphingomyelins were significantly greater at most corresponding cell stages than that of ¹⁴C-oleic acid (P<0.05) but the radioactivity of ¹⁴C-oleic acid recovered in inositol or serine phosphatides, lysophosphatidylcholines, monoglycosylglycerides was significantly higher than that of ³H-palmitic acid at almost every corresponding cell stage (P<0.05). These results demonstrated that the patterns of incorporation and distribution of double fatty acids in various lipid species were significantly different from those of the same single fatty acids in our previous report.