Cloned mouse embryos display a marked preference for glucose containing culture media, with enhanced development to the blastocyst stage in glucose containing media attributable mainly to an early beneficial effect during the first cell cycle. This early beneficial effect of glucose is not displayed by parthenogenetic, fertilized, or tetraploid nuclear transfer control embryos, indicating it is specific to diploid clones. Precocious localization of the glucose transporter SLC2A1 to the cell surface is also seen in cloned embryos, as well as increased expression of glucose transporters, and increased uptake of glucose at the one-cell and two-cell stages. To examine the role of glucose in early cloned embryo development, we examined glucose metabolism and associated metabolites, as well as mitochondrial ultrastructure, distribution, and number. Clones prepared with cumulus cell nuclei displayed significantly enhanced glucose metabolism at the two-cell stage relative to parthenogenetic controls. Despite the increase in metabolism, ATP content was reduced in clones relative to both parthenotes and fertilized controls. Clones at both stages displayed elevated concentrations of glycogen compared to parthenogenetic controls. There was no difference in mitochondria number, but clone mitochondria displayed ultrastructural alterations. Interestingly, glucose availability positively affected mitochondrial structure and localization. We conclude that cloned embryos may be severely compromised in ATP-dependent processes during the first two cell cycles, and that glucose may exert its early beneficial effects via positive effects on the mitochondria.