Since 1996, seven genetic mouse models have been reported to show increased lifespan: Ames and Snell dwarf mice, the 'little mouse' (Ghrhr(lit/lit)), mice null for either growth hormone receptor/binding protein (GHR/BP(-/-)) or p66(shc) (p66(shc-/-)), mice heterozygous for the IGF-I receptor (Igf1r(+/-)), and fat-specific insulin receptor knockout mice. In this article, we describe and evaluate these mouse models with respect to their relevance for aging studies. While these seven genetic models all show a significant increase in lifespan, issues of sample size and animal husbandry procedures require further evaluation before firm conclusions can be drawn on the reproducibility of life extension in most of these mouse models. Because data on the age-related pathology and physiological functions are lacking for all of the models, except the dwarf mice, it is too early to conclude that aging is retarded in these mouse models. However, these mouse models are already providing new information about the mechanism underlying mammalian aging.