The life histories of many vertebrates include complex, postembryonic developmental pathways that involve morphological and physiological changes that adapt juveniles to a new habitat. A survey of such developmental pathways, including lamprey metamorphosis, salmonid smoltification, and anuran metamorphosis, reveals a common strategy of lipid metabolism consisting of two distinct phases. The first phase is characterized by lipid accumulation in storage sites and results from lipogenesis prevailing over lipolysis. The second phase is characterized by Hpid depletion from storage sites and results from lipolysis prevailing over lipogenesis. Regulation of lipid deposition and lipid mobilization is essential for ensuring availability of lipid during times of need. Lipogenesis is promoted by insulin and, in lamprey and anurans, also by thyroid hormones. Lipolysis is promoted by a number of hormones, including prolactin, growth hormone, adrenocorticotropic hormone, corticosteroids, somalostatins, and thyroid hormones. The coordinate regulation of development-associated changes in lipid metabolism results from interactions among hormones and other internal and environmental cues.