Aging is both a natural and inevitable biological process. With advancing age, the kidneys undergo anatomical and physiological changes that are not only the consequences of normal organ senescence but also of specific diseases (such as atherosclerosis or diabetes) that occur with greater frequency in older individuals. Disentangling these two processes, one pathologic and the other physiologic, is difficult. In this review we concentrate on the glomerular structural and functional alterations that accompany natural aging. We also analyze how these changes affect the identification of individuals of advancing age as having chronic kidney disease (CKD) and how these changes can influence prognosis for adverse outcomes, including all-cause mortality, end-stage renal disease, cardiovascular events and mortality, and acute kidney injury. This review describes important shortcomings and deficiencies with our current approach and understanding of CKD in the older and elderly adult.