Spiny mice are useful in regenerative research and as a model for precocial animals. In the present study, we investigated the taxonomic status of the Aco strain, which is derived from spiny mice of an unidentified species. Although this Aco strain has been tentatively considered A. cahirinus species, it was distinguished from this species based on conventional and G-banding chromosomal patterns of this strain. Subsequently, we determined the nucleotide sequence of the mitochondorial gene cytochrome b (Cyb) andconstructed a molecular phylogenetic tree. We found that the Aco strain belongs to the same clade as A. dimidiatus. Based on this molecular analysis, we concluded that the Aco strain of spiny mice should be considered A. dimidiatus.