The population worldwide is aging rapidly and the understanding of physiological changes associated with aging is a key tool for answering the biomedical and social needs of elderly people. The aim of the present review is to describe the main morphological and functional changes of the cardiovascular system, central nervous system, kidney, skeletal muscle and glucose metabolism associated with normal aging. Clinical and experimental studies show that cardiovascular aging is associated with a reduction of muscular cells and wall distensibility. The cardiac ejection fraction does not change. With aging, the kidney develops vascular and glomerular sclerosis, with moderate reduction in glomerular filtration rate, lower concentration/dilution ability and a reduction of vitamin D synthesis. Aging associates with reduced brain volume, but without a generalized loss of neurons or dendritic arborization. Elderly people presents reduced attention span, lower work memory and motor impairment. There is a decrease in skeletal muscle mass, with increased in adipose infiltration associated with progressive force loss. The proportion of body fat, particularly the visceral fat, could play a role in the development of insulin resistance, which associated with a decrease in pancreatic beta cells may lead to the development of diabetes mellitus. The available evidence shows important morphological and physiological changes associated with aging. The knowledge of morphological characteristics and functional capabilities of middle age adults may not be extrapolated to elderly people. The identification of changes due to normal aging is hampered by the high variability among individuals and the high prevalence of co-morbidities.