Even though numerous questions with regard to the pathogenesis of athero sclerosis have not yet been answered, the accumulated evidence indicates significant regression of lesions in experimental animals. This is discussed extensively in this monograph, as are the mechanisms involved in regression of lesions. Whether human atherosclerosis has the potential for regression appears to be the most important, but at the same time the most difficult question to answer. Contrary to experimental atherosclerosis in animals, which can be produced and which can regress within a few months, human lesions...