Syndromes of aging are classified according to the rate of their development and the sequence of aging of different systems within an organism. Syndromes of aging are characterized by individual and populational specifics. Determination of syndromes of accelerated aging or retarded aging permits the prediction of age pathology development and life span. Comparison of aging peculiarities in animals with different species-specific life spans permits the definition of species-specific changes, chronobiological changes that correlate with chronobiological age, ontobiological changes that correlate with biological age, and parameters that do not change with age. Different correlation of the above parameters forms the basis for species-specific variations in the aging process. Neurohumoral shifts observed in aging are identical to stress effects, and therefore may be referred to as the stress-age syndrome.