The metabolic rate of Crocodylus johnstoni eggs was measured through incubation at 29° and 31° C, and in C. porosus eggs at 30° C. The pattern of metabolic rate in both species ispeaked, similar to patterns recorded in other embryonic reptiles that develop in hard:shelled (cleidoic) eggs. Maximum $\dot{V}_{O_{2}}$ occurs when incubation is less than 90% complete. Total oxygen consumed ($V_{O_{2tot}}$) by C. johnstoni eggs is higher at 29° C (86.2 mL·g⁻¹ [STPD]) than at 31° C (77.8 mL· g⁻¹[STPD]). Yolk-free mass of 29° C hatchlings is, however, higher, so that mass-specific $V_{O_{2tot}}$ is similar at both temperatures. The prehatch peak in metabolic rate may reflect a development mode evolved in reptiles nesting in highly variable environments. An exponential pattern of growth early in incubation followed by a period of limited growth and declining energetic demands combine to provide a flexible hatching schedule that can be matched to environmental conditions without incurring major energetic costs.