The dogs and cats, treated at the Clinic of Internal Medicine of the University of Munich since 1983 show a tendency to a higher age of life; this is true especially in cats. The age structure of the dog population expresses a tendency to an increase of older individuals since a longer time period, whereas in the cat population this development could not be verified before the year of 1987. The results of this examination require an intensive work on the problems of increasing age, especially with those of multimorbidity, the preponderance of chronic diseases, prophylaxis, nutrition, and posture.