An Irish, or American Irish, rat has a full-colored body with a single round spot on the lower part of the belly. All four feet should also be white, and up to a quarter of the tail. The marking should be of good size, but not extend to the sides or the chest of the rat.

H/h

A single recessive on the Hooded (H) locus, this is the same genetic description as Berkshire, but with extra modifiers to decrease the amount of white, which have not been genetically described.

AFRMA (as Irish)

"Irish rats may be shown in any recognized color. The top color is to be judged as to the respective color. Distinctive markings are the white underside, with four white feet and a white tail tip. The under marking should be a pure clean white, of moderate size and as even in shape as possible, not extending onto the legs, sides or chest. The white feet should resemble the stops on a Dutch rabbit. The tail should be colored for most of its length, with a white tip of no more than one-fourth of its total length."

RSA (as Irish)

"White markings on lower abdomen with four white feet and white tail tip.  The marking shall be pure clean white, of moderate size and as even in shape as possible, not extending onto the legs, sides or chest.  The tail shall be tipped in white no more then one-fourth its total length.  The body shall conform to a recognized color."

RatsPacNW

"Symmetrical white spot on belly of uniform size.  Four white feet to ankles and white tip tail to no more than 1/4 its length."

URS

"The body of the rat shall be of any standardized color. The feet, tail-tip and lower belly marking are to be white; white should not extend upward to half the length of the tail, nor up the legs. The abdominal marking to be as round as possible, of even shape and moderate size, not extending to the chest or legs."