The Bullmastiff was developed in England by gamekeepers for protection against poachers. The foundation breeding of the modern pure-bred was 60 per cent Mastiff and 40 per cent Bulldog. It is a guard and companion dog, and should be loyal, obedient, and thus suitable for training.

The Bullmastiff is a powerfully built, symmetrical dog, showing great strength and activity, but not cumbersome; upstanding and compact in appearance, with breadth and depth of skull and body, the latter set on strong, sturdy, well-boned legs. The height measured vertically from the ground to the highest point of the withers, should nearly equal the length measured horizontally from the forechest to the rear part of the upper thigh, and should slightly exceed the height at the hips. Bullmastiffs bitches are feminine in appearance, of somewhat lighter bone structure than the male, but should still convey strength. Faults: (S) Lack of balance. Poor or light bone structure. (M) Lack of muscular development. Ranginess.

The Bullmastiff should be bold, fearless and courageous, a dependable guard dog; alert and intelligent. Faults: (S) Viciousness. Shyness. (Such dogs should not be used for breeding.) (M) Apathy and sluggishness.

The Bullmastiff height at the highest point of the withers - Dogs, 25-27 inches (63-69 cm); Bitches, 24-26 inches (61-66 cm). Weight - Dogs, 110-130 lb. (50-59 kg); Bitches, 100-120 lb. (45-55 kg). It is important that weight be in proportion to height and bone structure, to ensure balance. Faults: (S) Over maximum height. Under minimum height. (M) Over maximum weight. Under minimum weight.

The Bullmastiff coat should be short and dense, giving good weather protection. Faults: (S) Long, soft coat. (M) “Staring” coat, which means poor condition. Colour: any shade of red, fawn or brindle, but the colour to be pure and clear. A small white marking on chest permissible but not desirable. Faults: (S) White markings other than on chest. (M) Black shading on body, legs or tail (of reds or fawns).

The Bullmastiff skull should be large, equal in breadth, length and depth, with a fair amount of wrinkle when the dog is interested; well-developed cheeks. The skull in circumference may measure the height of the dog. Forehead flat, with furrow between the eyes. Stop definite. Faults: (S) Narrow skull. Shallow skull. (M) Domed forehead. Insufficient stop. Muzzle should be short, broad and deep, in the same proportion as the skull. The distance from the tip of the nose to the stop should not exceed one-third of the length from the tip of the nose to the centre of the occiput. Broad under the eyes and nearly parallel in width to the end of the nose; blunt and cut off square, appearing in profile in a plane parallel to the line of the skull. A black mask is essential. Bullmastiff's nose should be black, flat, and broad with widely spreading nostrils when viewed from the front. Flews not too pendulous. The lower jaw broad. Faults: (S) Muzzle too long, too narrow, pointed or lacking in depth. Muzzle too short; nostrils set on top; nose pointed, upturned or laid back; lower jaw narrow. (M) Lack of wrinkle; flews too pendulous. Bullmastiff's teeth preferably level bite or slightly undershot. Canine teeth large and set wide apart; other teeth strong, even and well placed. Faults (S) Teeth overshot. Teeth more than 1/4 inch (.6 cm) undershot. Wry mouth. (M) Irregular or poorly placed teeth. Small teeth. Eyes dark or hazel, and of medium size; set apart the width of the muzzle. Faults: (M) Light eyes. Eyes too close together, too large, too small. Ears V-shaped and carried close to the cheeks; set on wide and high, level with the occiput, giving a square appearance to the skull which is most important. They should be darker in colour than the body, and the point of the ear, when alert, should be level with the eye. Faults: (S) Rose ears. (M) Ears too long or too short. Lack of darker colour.

Bullmastiff's neck should be well arched of moderate length, very muscular, and almost equal in circumference to the skull. Faults: (S) Neck too short; too long. Neck weak and scrawny.

Body compact. Chest wide and deep, with ribs well sprung and well set down between the forelegs. Back short and level. Loins wide, muscular; croup slightly arched, with fair depth of flank. Faults: (S) Body too long. Shallow chest. Narrow chest. Lack of ribspring. Sway back. Roach back. Tip of hip bone higher than withers. (M) Too much tuck-up. Tail set on high, strong at the root and tapering to the hocks. It may be carried straight or curved. Faults: (S) Screw tail. Crank tail. Tail set too low. (M) Tail carried hound fashion. Too long. Too short. Too heavily coated.

The dog should be moved in the ring at a sufficient speed to show fluidity of movement and not at a slow walk. Faults: (S) Rolling, padding or weaving when gaited. Any crossing movement, either front or rear. Stilted and restricted movement. (Dogs with structural weakness as evidenced by poor movement should not be used for breeding.)