The total lipid content, amount of phospholipid, proportions of major polar and neutral lipid classes, and the overall fatty acid composition were examined in Xenopus laevis embryos. No obvious differences were observed in any of the parameters between fertilization and hatching or between eggs produced by different females. The average lipid content per egg was 113 mug, 31.6 mug of which was phospholipid. The major phospholipids were phosphatidylcholine and sphingomyelin. The major fatty acids were palmitic and oleic acids, but polyunsaturated fatty acids were also present in substantial amounts. The results suggest that significant de novo synthesis of lipids does not occur until after hatching.