The status of Leiosty1a in the Iberian peninsula and NW. Africa is reviewed. Examination of material of Leiostyla anglica from Britain and Ireland showed that shell characters such as size, shape, colour and development of apertural teeth were variable within and between populations. Shells of Leiosty1a numidica from Algeria were also found to be variable. As the main distinguishing characters are shape of the shell and the absence of a basal plica and as both characters are variable, it is difficult to justify the separation of Leiosty1a numidica. Factors influencing the range of Leiostyla in NW. Europe are discussed.