• I now have a pack of 4 dogs.  Out of those 4 dogs, 3 of them are breeds known for dog aggression.  So far, all of my dogs are living in harmony.  Dog aggression can exist in any breed, one bad experience can bring that on.  I have an American Bulldog mix, a German Pinscher, a Rat Terrier & a Cimarron Uruguayo.  Although mastiff dogs are known to be dog aggressive, they can also live in harmony with their own family pack.  The dog aggression may just show with dogs outside the home (like my dogs do).  My dogs are fine with each other, but they aren't very fond of other dogs that don't live with us.  I'm OK with that, I'm not one of those people that believe in doggy friends.  As long as they are fine in my house, I don't care about external doggy friends.  I keep my dogs on a leash at all times & keep my distance from other dogs.

    Although dog aggression is something to be mindful of, I don't consider it a deal breaker since any dog can decide they don't like other dogs at any given time.

    I agree with the previous poster who said go with the breed you like the most & do lots of training.  Go with the one you know you can live with. :-)