The origins of the Chihuahua are not known. The modern dog was, however, discovered in Mexico's Chihuahua state in 1850. Most of today's dogs are descended from the original 50 taken to the USA.

Evidence in stone carvings of the Toltec people firmly establishes that the Chihuahua was in Mexico in the ninth or tenth century. Written records also indicate that the dog was important in the religious and mythological life of the later Aztecs.

Chihuahuas may be longhaired or smooth-coated. The smooth coat is considered to be the original variety. The longhaired dogs were created in the early 20th century possibly by crossing with longhaired toy breeds such as the Papillon and Pomeranian.

BODY TYPE:

• A sturdy breed but exceedingly tiny.
• Height: 6-9 inches (at shoulder).
• Weight: 2-6 pounds. Anything over 6 pounds is disqualified.
• Erect, wide-set ears are not altered.
• Gently curved tail held erect but not over back (called a sickle tail) is not altered.

PERSONALITY:

• The ultimate lap dog. Bred to be a charming companion, the Chihuahua is extremely affectionate toward those it considers family. Reserved, however, with strangers.
• Temperamental.
• Easily trained for the most part, although difficult to housebreak.

COAT:

• In the smooth-coated variety the hair is short, soft and glossy.
• The hair is longer around the neck creating a "ruff."
• All colors and combinations of colors are allowed. Mexican fanciers favors a jet black dog with tan markings or a black and white spotted one. Solid color dogs are preferred in the United States.
• Minimal grooming.

TIPS:

• The Chihuahua is the smallest breed of dog according to the Guinness Book of Records. One full grown specimen weighed in at ten ounces.
• Sensitive to the cold, the Chihuahua shivers a lot. It also shakes when excited or nervous.
• Low exercise requirements make this breed ideal for apartments and older people.
• Not recommended for small children because of its small and fragile body.
• Long lived breed
• High pitched bark. They will keep up an alarm until you investigate, making them an excellent alarm system.
• Chihuahuas recognize and prefer their own kind. However they get along beautifully with other breeds of dogs --from Beagles to Great Danes IF properly introduced or raised together!
• Majority of these little tykes are wonderful with cats.

HEALTH CONCERNS:

• The tiny bones are easily broken.
• The soft spot on the skull called a molera does not always close and even a mild blow to this area can kill.
• Slipped stifle or dislocated kneecaps may cause dogs to have a hopping gait.
• Epilepsy.
• Gum diseases in older dogs.
• Chihuahuas with overly large, round shaped heads (a style of these dogs --but not the breed standard or typical) may have trouble whelping.
• Chihuahuas may often require Cesarian sections and the average litter is 2-4 puppies.

source: Dog.com Breeds - Chihuahua (Smooth Coated);
http://www.dog.com/breed/Chihuahua-smooth-coated.asp