Mitochondria have occupied a central place in theories on the underlying cellular mechanisms of eukaryotic aging for several decades and much debate has ensued regarding the role of oxidative stress and mitochondrial genomic damage in these processes. Mouse models with greatly enhanced mitochondrial mutagenesis have produced dramatic aging-like phenotypes but recent results have led some to reassess whether such models are relevant to naturally occurring aging mechanisms. Here, we discuss the evolving insight that may be gained from these models regarding the contribution of mitochondrial DNA mutations to aging.