The following account of the non-marine Mollusca of the Island of Sumatra, the second largest of the Greater Sunda Islands (surface 440.000 km2) is based on the following collections: 1. Zoological Museum, Amsterdam, including the material collected by Prof. Max Weber, Dr. L. P. de Bussy, Jhr. Dr. F. C. van Heurn, Prof. J. C. van der Meer Mohr, Dr. E. Jacobson, and many others. 2. Rijksmuseum van Natuurlijke Historie, Leiden. 3. Museum Zoologicum Bogoriense, Bogor (Java). 4. Naturhistorisches Museum, Basle (Switzerland). 5. Zoologisches Museum, Zürich (Switzerland). 6. Muséum d’Histoire Naturelle, Geneva (Switzerland). 7. Naturmuseum Senckenberg, Frankfurt am Main (Germany). 8. Mr. J. P. van Niel, who lived in Sumatra from 1951 to 1956 and made great efforts to collect molluscs in his leisure time. This material has been presented to the Zoological Museum, Amsterdam. 9. Various private cabinet owners in the Netherlands and one in Switzerland who received their material from relations overseas. In the list of localities these collections will be referred to by the following symbols: ZMA Zoological Museum, Amsterdam RMNH Rijksmuseum van Natuurlijke Historie, Leiden MBo Museum Zoologicum Bogoriense, Bogor MBa Naturhistorisches Museum, Basel MZh Zoologisches Museum, Zürich MGv Museum d’Histoire Naturelle, Geneva SMF Senckenberg Museum, Frankfurt Nl Mr. J. P. van Niel Br Mr. A. C. van Bruggen, Leiden Bt Mr. L. J. M. Butot, Haarlem By Dr. P. Bohny, Basle Dr Mr. J. Drijver, Wageningen Ls Dr. F. E. Loosjes, Wageningen Nb Mr. W. H. Neuteboom, Heemskerk Sl Mr. L. van der Slik, Rotterdam Vm Mr. L. A. W. C. Venmans, Moergestel