Companion Dog refers to a title offered by the American Kennel Club

American Kennel Club

The American Kennel Club is a registry of purebred dog pedigrees in the United States. Beyond maintaining its pedigree registry, this kennel club also promotes and sanctions events for purebred dogs, including the Westminster Kennel Club Dog Show, an annual event which predates the official...

 for dog obedience

Obedience training

Obedience training usually refers to the training of a dog and the term is most commonly used in that context. Obedience training ranges from very basic training, such as teaching the dog to reliably respond to basic commands such as "sit", "down", "come", and "stay", to high level competition...

. Other kennel club

Kennel club

A kennel club is an organization for canine affairs that concerns itself with the breeding, showing and promotion of more than one breed of dog...

s also offer similar CD titles. To earn an American Kennel Club CD title, a dog must receive a qualifying score of 170 out of 200 in the Novice

Novice

A novice is a person or creature who is new to a field or activity. The term is most commonly applied in religion and sports.-Buddhism:In many Buddhist orders, a man or woman who intends to take ordination must first become a novice, adopting part of the monastic code indicated in the vinaya and...

 obedience class at three separate, American Kennel Club-licensed obedience trials, and by three different judges.
Dogs that receive three qualifying scores competing in the more challenging Open class at three different obedience trials

Obedience trial

An obedience trial is a dog sport in which a dog must perfectly execute a predefined set of tasks when directed to do so by his handler. According the American Kennel Club obedience regulations...

, and by three different judges, can be awarded the American Kennel Club Companion Dog Excellent (CDX) title.

The preceding two titles go on the end of the dog's registered name.