The increasing life expectancy in humans--at least in the developed countries--including all medical, social, and political consequences is a generally accepted phenomenon at the end of this century. In earlier examinations it could be noticed that also in dogs and cats a remarkable increase of the life span seems to occur in the last 15 years (Beelitz 1988; Danckert and Kraft 1997; Davis 1996; Eichelberg and Seine 1996; Goldston 1989; Kraft 1978, 1990, 1997 a-c; Kraft and Danckert 1997; Kraft et al. 1989; Pauling 1990; Trimborn 1990). If this is true, it could have a series of consequences not only for the veterinary practice but also for the comparative medicine. The aim of this paper was to examine a population of dogs and cats to find out, if the life span of these companion animals really increases and the consequences it may have for medical care. The following criteria were examined: (1) the distribution of the age of the dogs and cats at their last presentation as out-patients (2) the change of the age at which the animals died on an average (3) the influence of the breed on the life expectancy (4) the relation of the sex and expectation of life (5) age related multimorbidity (6) the appearance of the most common organ diseases and functional disturbances during the life span