The biggest breed of dog depends on whether you’re talking about weight or height.  The heaviest dog is probably the mastiff, which can weigh over 200 pounds.  It is not surprising that mastiffs were originally bred to be … watchdogs!  The ancient Romans also used them to fight bears, lions and tigers!  What’s with the Romans and their love of blood? 

In spite of their size, however, most mastiffs are gentle and friendly.

The tallest dog is the Irish wolfhound, which measures up to three-nd-one-half feet tall at the shoulder when standing on all fours.  On his hind legs, the Irish wolfhound can stand over seven feet tall – considerably bigger than most people.  As his name suggests, the Irish wolfhound was originally used to hunt wolves in Ireland! 

If you re thinking of getting one of these breeds or any other very large dog, such as a Saint Bernard, Newfoundland or Great Dane as a pet, you should make sure you have enough space for the animal to exercise.  Big dogs are usually not very happy in apartments or houses with small back yards.  You must also have enough strength to walk your dog, and enough money to feed him:  the biggest breeds will eat several hundred dollars’ worth of food each year!