The amateur Jack Russell terrier breeders under the guidance of the English judge Eddie Chapman published the first standard before the British Kennel Club recognised the breed:

Characteristics
The terrier must present a lively, active and alert appearance. It should impress with its fearless and happy disposition. It should be remembered that the Jack Russell is a working terrier and should retain these instincts. Nervousness, cowardice or over aggression should be discouraged and it should always appear confident.

General appearance
A sturdy, tough terrier, very much on its toes all the time, measuring between 9" and 15" at the withers. The body length must be in proportion to the height and it should present a compact, balanced image, always being in a solid, hard condition.

Head
Should be well balanced and in proportion to the body. The skull should be flat, of moderate width at the ears, narrowing to the eyes. There should be a defined stop but not over pronounced. The length of mussle from the nose to the stop should be slightly shorter than the distance from the stop to the occiput. The nose should be black. The jaw should be powerful and well boned with strongly muscled cheeks.

Eyes
Should be almond shaped, dark in colour and full of life and intelligence.

Ears
Small "V" shaped drop ears carried forward close to the head and of moderate thickness.

Mouth
Strong teeth with the top slightly overlapping the lower.

Neck
Clean and muscular, of good length, gradually widening at the shoulders.

Forequarters
The shoulders should be sloping and well laid back, fine at points and clearly cut at the withers. Forelegs should be strong and straight boned with joints in correct alignment. Elbows hanging perpendicular to the body and working free of the sides.

Body
The chest should be shallow, narrow and the front legs set not too widely apart, giving an athletic, rather than heavily chested, appearance. As a guide only, the chest should be small enough to be easily spanned behind the shoulders, by average size hands, when the terrier is in a fit, working condition. The back should be strong, straight and, in comparison to the height of the terrier, give a balanced image. The loin should be slightly arched.

Hindquarters
Should be strong and muscular, well put together with good angulation and bend of stifle, giving plenty of drive and propulsion. Looking from behind the hocks must be straight.

Feet
Round, hard padded, of cat-like appearance, neither turning in nor out.

Tail
Should be set rather high, carried gaily and in proportion to body length, usually about 4" long, providing a good hand hold.

Coat
Smooth, without being so sparse as not to provide a certain amount of protection from the elements and undergrowth. Rough or broken coated, without being woolly.

Colour
White should predominate with tan, black or brown markings.

Gait
Movement should be free, lively, well co-ordinated with straight action in front and behind.

Please note
For showing purposes terriers are classified in two groups - 9" to 12" - over 12" and up to 15".

Old scars or injuries, the result of work or accident, should not be allowed to prejudice a terrier's chance in the show ring unless they interfere with its movement or with its utility for work or stud. Male animals should have two apparently normal testicles fully decended into the scrotum.

A Jack Russell Terrier should not show any strong characteristics of another breed. 

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On January 1990 the British Kennel Club adopted the standard of the breed of the Parson Jack Russell Terrier Club and recognised this club as the official representative of the breed. It entrusted to it the responsibility to gather all the owners of Parson Jack Russell Terriers who held pedigree papers delivered by the club for at least three generations. This pedigree became official after recognition by the Kennel Club.