Even if this breed was developed solely in the United States, the breedbase was English; Bulldogs and Bullterriers, together with some dogs of unknown ancestry.
This lively, intelligent and friendly dog is the lightest member of the Molosser family. It should be compact built, have a square appearance. The smooth and shiny coat should be brindle, black or reddish black, with white marks on the muzzle, chest and over the eyes. Markings on the neck, feet and lower parts of the legs is optional.
The ears are small, carried erect, either natural or cropped to conform to the shape of the head and situated as near to the corners of the skull as possible.
The Boston Terrier is bred for being an indoor dog. It does not tolerate a lot of heat or cold.
The breed has prominent eyes, and can prone to corneal injuries.

The Boston Terrier is a dog of about 38-43 cm. (15-17 in) height.
It is devided into three weight sizes:
Below 15 lb.(6.8 kg).
Over 15 lb. (6.8 kg.) and below 20 lb. (9.1 kg).
Over 20 lb. (9.1 kg.) and not to exceed 25 lb. (11.4 kg).