The term dog breed may also be used to refer to natural breeds or landraces, which arose through time in response to a particular environment which included humans, with little or no selective breeding by humans. Such breeds are undocumented, and are identified by their appearance and often by a style of working. Ancient dog breeds are some of the modern (documented) descendants of such natural breeds.

Dog breeds are not scientifically defined biological classifications, but rather are groupings defined by clubs of hobbyists called breed clubs.

A dog breed is represented by a sufficient number of individuals to stably transfer its specific characteristics over generations. Dogs of same breed have similar characteristics of appearance and behavior, primarily because they come from a select set of ancestors who had the same characteristics. Dogs of a specific breed breed true, producing young closely similar to the parents. An individual dog is identified as a member of a breed through proof of ancestry, using genetic analysis or written records of ancestry. Without such proof, identification of a specific breed is not reliable. Such records, called stud books, may be maintained by individuals, clubs, or other organizations.

• Herding Group (2,287)
• Hound Group (1,454)
• Livestock Guardian Dogs (222)
• Molosser Group (1,552)
• NonSporting-Utility Group (887)
• Primitive Group (31)

• Spitz Group (124)
• Sporting-Gundog Group (1,881)
• Terrier Group (1,020)
• Toy Group (1,055)
• Working Group (1,132)

• Experimental Breeds and Hybrids (86)

• Breeders and Kennels (41)
• Clubs (1)
• Rescues and Shelters (1)

• Walters and Shackles Guide to Dog Breeds
  gardening-uk.com
  A British guide to dogs, with histories of breeds, and watercolour illustrations. [not suitable for all browsers]
• Dog Breed Pictures
  puppypoopy.com
  Large gallery of pictures organized by breed.
• Best In Show Web Ring
  webring.com
  Webring for owners or breeders of Best In Show dogs.

• Usenet rec.pets.dogs - news: - Google Groups