Changes in biochemical composition during the transition from eggs to larvae in the blue crab Callinectes sapidus were documented. The amounts of proteins, lipids, and carbohydrates decreased from newly formed embryos (stage I) through prehatching embryos (stage II) to newly hatched larvae (stage III; P < 0.05), but the water content increased significantly from stage I to stage II (P < 0.05). Total saturated fatty acid increased significantly from stage I to stage II (P < 0.05), then the content of total saturated fatty acid in stage III decreased to a level similar to that in stage I. In contrast, total monounsaturated fatty acid, n3/n6, and docosahexaenoic acid-to-eicosapentaenoic acid ratios decreased significantly from stage I to stage II (P < 0.05), whereas these variables remained unchanged in stage III. The level of n6 polyunsaturated fatty acid increased significantly from stage I to stage II (P < 0.05) and then stabilized subsequently during stage III. Lipid class analysis revealed that the percentage of triglyceride decreased significantly from stage I to stage III, whereas the proportion of Cholesterin increased (P < 0.05). Phospholipids decreased significantly from stage I to stage II (P < 0.05), then returned to stage I levels during stage III. These data suggest that the embryos in stage II and stage III required more energy compared with those in stage I.