The research purpose is a comparative characteristic of lymph nodes structure at natural (physiological) aging of Wistar rats and premature of OXYS rats. We used a morphological method of a research. Age changes of lymph nodes structure differ at rats of OXYS and Wistar. The age-induced changes of lymphoid tissue of Wistar and OXYS rats differ with type of the immune response and morphological variant of lymph nodes structure. The immune response on humoral type is formed in mesenteric and inguinal lymph nodes, and the immune response on cellular type is formed in the tracheobronchial lymph node. The sizes of compartments of lymph nodes reach the greatest development at three-months age of Wistar rats, but it is not observed at OXYS rats. Lymph nodes compartments undergo involution when aging. We noted reduction of structures of cortical substance, especially lymphoid follicles and a paracortex, and expansion of medullary substance in lymph nodes. Lymph nodes are subject big morphological changes at OXYS rats, than at old rats of Wistar. Observed changes of structure of lymph nodes have the region-dependent character and can be considered as aging predictors with the indication on weakening of a drainage and immune function of lymph nodes.