[WHATNEXT?]

Yes, most aggression I have seen is in the smaller breeds, especially those you mention.

We have given him all our love and a good home -- but to no avail. He has some amazing good traits.....

[Judith Anne]

Our dog, an American Mastiff (from the English mastiff breeder Fredericka Wagner of Flying W Farms, has an ironclad lifetime temperament guarantee.

He was big bucks, but he is worth it. Extremely gentle. This is the most intelligent and enjoyable animal we have ever owned. He's one year old.

Here's the site with recommendations from owners:

http://www.flyingwfarms.com/amastiff/thumbs.html

[angkor]

There's always going to be a baseline good temperament for Sheps after 100 years of breeding.

But dominant aggressiveness toward the owner is not part of that baseline.

Like I said, its genetics. Just as much a genetic flaw as bad hips, but one that can cause you big problems down the road.

Take the dog to a vet, as others have said. But this sounds way outside the bounds of desirable behavior.

You might also take a look at the AKC web site, which has an excellent database of all registered breeds and their behavioral profiles.