The known records of the occurrence of the erythristic polecat in Wales (the only part of Great Britain from which it has been noted) are listed and mapped, and show that this form is confined to a very limited area of West Wales, mainly along the coast of Cardigan Bay. The normal form has during the same period been widely distributed over most of Central Wales though thinning out towards the periphery, and has occurred also in one or two of the English border counties. It is suggested that the establishment and spread of the red polecat is of recent date. A similar limited distribution‐area of concentration of an erythristic recessive mutation in the polecat has been noted in western Russi