There are seven localities where the slipper limpet, Crepidula fornicata, has been recorded in Irish waters. Most introductions to Ireland were with transfers of oysters from America, Britain and mainland Europe. These records are discussed in relation to the expansion of the slipper limpet’s European range. Populations may have become established in Kenmare and Clew Bays, but following the prolonged cold period in 1963 no living populations have survived. In 1993, following an European Community directive on free trade, the Pacific oyster, Crassostrea gigas, was imported from France and was found to carry C. fornicata.