A chemical composition for use in controlling the population of free-roaming, sexually mature male dogs. The chemical sterilant is injected in a manner that the dog's appearance and secondary male sexual characteristics are preserved such that the dog maintains its position in the hierarchy of the free-roaming dogs while not contributing to the number of puppies produced. A reduction in the number of free-roaming dogs reduces the number of human victims of dog-bite acquired rabies. Because the appearance and nature of the sterilized dog is substantially unchanged, the chemical composition is acceptable to the human community that the dog habitats.