Aging is accompanied by a decline in the effectiveness of a number of immun
e functions. This has been termed "immunosenescence". Changes identified to
date suggest that the major defects reside in the T cell immune compartmen
t. Recent research also suggests that alteration in B cell and other immune
cells may play an important role in defining the immune competency in the
elderly. These changes have been linked to reduced responses to immunizatio
n, and increased rate of infection, cancer, and mortality in aging. In the
era of the aging baby boomers, it is important for all clinicians to unders
tand these changes and their implications.