Male rats in one group were 5-6 months of age and in another group 20-24 months. These were allowed to copulate under two conditions. At one occasion they mated without any interference of the experimenter and at another they were handled approximately twice a minute. The older males, although sexually less vigorous than the younger males when copulating under non-handling conditions, when handled became quite as active as the younger males. It was concluded that the mating activity is determined not only by sexual stimuli but by non-sexual stimuli as well, and that the decrease in sexual activity characteristic to the old rat can be compensated for by an increase in the non-sexual sensory stimulation of the animal.