Although thousands of articles and hundreds of books on aging have been published, only a small percentage of this material has dealt with anatomy, particularly at the fine­ structural level. It was with this in mind that Aging and Cell Structure was conceived. Volume 1 of Aging and Cell Structure was published in 1981 and represented a current compilation of information, concentrating at the electron microscopic level, on morphological changes which occur in cells and tissues as they age. The present volume completes the two-volume set. While Volume 1 highlighted structural changes occurring in the aging nervous system, Volume 2 centers its efforts on studies of in vitro aging. Chapters on other subjects are included as well. These include age-related changes seen in neuromuscular junctions, oral tissues, and the pancreas. Although these two volumes represent a very small part of the published infor­ mation on experimental gerontology, their approach is rather unique because they focus on anatomy, perhaps the most basic of all the biomedical sciences. Because many dif­ ferent tissue types are examined, we begin to see recurrent, definitive patterns in the aging cell which may not be fully apparent from studies taking one cell type at a time. This becomes even more evident in the present volume where changes seen in popula­ tions of cells grown in culture-isolated from hormones or nervous impulses from other body areas-are found to be similar to those changes found in vivo.