This review will briefly describe the different components of the IGF system and then discuss past and current literature regarding IGF and aging, with a focus on cellular senescence, model organisms of aging, centenarian genetics, and 3 age-related diseases—pulmonary fibrosis, Alzheimer disease, and macular degeneration—in appropriate murine models and in humans. The gene discussed is IGF1; the disease is early-onset autosomal dominant Alzheimer disease.