A study of the Caecidae (Gastropoda Prosobranchia) from the European Atlantic coast, the Canary Islands, as well as the Mediterranean has resulted in about 26 different names for species described by various authors during the last 150 years. Difficulties encountered in identifying species of this family have been summed up recently by Moore (1968: 39): “It is at the generic and specific level that most difficulty is encountered. Some species have considerable variation, and this, combined with the three stages of growth and differences due to wear, has brought on a great deal of confusion. ... Inability to understand variation in a species resulted in some being named several times from the same small bottom sample. The varying quality of his [=De Folin’s] figures also compounded the confusion”. It is with these remarks in mind that a revision of the Caecidae from the area indicated earlier was undertaken. The results as published in this paper are based on a critical literature survey on the one hand and the study of all relevant material in the collections of De Folin (Muséum National d’Histoire Naturelle, Paris), Carpenter [British Museum (Natural History, London] and Jeffreys (National Museum of Natural History, Washington D.C., U.S.A.) and in some other collections. Acknowledgements are due to the various persons in charge of these collections for assistance during the present author’s visits. Apart from the collection of Caecidae of P.P. Carpenter, the British Museum also contains some samples of Chaster, whereas the Jeffreys collection in Washington contains a number of samples which were given to Jeffreys by De Folin and Monterosato. This could be ascertained by the fact that De Folin used a special type of blue slides to mount his specimens; some of these slides were also found in the Jeffreys collection with a species name in the handwriting of De Folin. Specimens originating from Monterosato could be identified by the fact that either the label mentioned this or the original label in the characteristic handwriting of Monterosato was still present.