Assuming that your female dog is spayed, it is best to add a male to your family. In general, female and male dogs get along better than dogs of the same sex—and when two dogs in the same household do not get along, it is most often a pair of the same sex. We’ve also seen that when two females disagree, they are more likely to inflict injury on each other during fights. To increase the likelihood that your new dog will get along well with your current dog, we recommend that both undergo basic obedience training. This will help keep them more controlled in potentially testy situations. Also, keep in mind that dogs most often fight over resources, such as food, beds, toys, bones and human attention. If you have a multiple pet household, it is wise to be careful when offering food, treats and edible toys, as you don’t want to provoke an unnecessary fight.