Traditionally, female and male dogs have usually been neutered at about six months old. Before the development of safe anaesthetics and surgical methods, it was believed that a nearly fully grown animal would cope better with the operation. However, increasing numbers of vets now like to neuter animals earlier than this. There is no evidence that such early neutering harms a dog's later health and physical development. Your vet will be happy to discuss with you the best time for neutering your dog.