A veteran K9 nicknamed "The Wonder Mutt" figures to be the favorite, but will he be taken out by the younger, hungrier competition? His challengers include a police dog with hundreds of narcotics arrests and a civilian trick dog who just might be the most talented tail-wagger in the whole field.

A third generation police K9, and a civilian underdog built for speed are among the pooches who face off in a competition that comes right down to the wire. Who will get the last woof?

A fur missile, a veteran K-9 named Murphy and a small civilian underdog compete.

Two civilian underdogs take on the professional pooches in an epic clash of K-9s, as a brash boxer and a peppy pit bull attempt to be leader of the pack

The youngest dog in the competition sets a fur-ious pace; the more experienced dogs must take matters into their own paws or a youngster will bring home all the biscuits.

Among the K9 combatants are a dog who once took down a crossbow-wielding creep, a pooch whose trainer is allergic to him, and a team with inspiration on their side. Who will emerge lick-torious?

It's raining cats and dogs, but the K-9 combatants show their gladiatorial spirit, battling through bad weather and tricky tunnels right down to the final seconds.

With some of the most decorated doggies ever to set paw on the K-9 combine, records may be broken.

The lineup raises burning questions such as if old can defeat young and if skill can beat experience.

A Doggle-wearing K-9 faces some tough competition including a Connecticut K-9 who's ready to declare war and cancer-surviving civilian underdog named Bruce.

Six winning K-9s and one champion underdog battle it out for $25,000 and the bragging rights for the ultimate title of "America's Top Dog."

A Hollywood superstar pup takes on a bird hunter, a talented pit bull goes up against a punk rock border poo, and two K9s named after movie villains face off.

A 17-pound underdog takes on a protective Czech shepherd, two K9s from the same department duke it out, a therapy dog goes against the smallest dog of the season, and in the Doghouse, one dog gets disqualified for the first time in Top Dog history.

A female K9 aims to dominate her male opponent; three Belgian Malinois give their handlers a workout; and an old contender shows up to prove that age ain't nothing but a number.

A frisbee-catching pro takes on a demo dog. A female K9 goes up against a tall dog.