The Fourth International Workshop on Spallation Materials Technology (IWSMT-4) took place on 8–13 October in Schruns, Austria. The present volume contains the proceedings of this workshop. 53 scientists from Europe, USA and Japan presented 44 papers covering a wide range of topics including the status of spallation target R&D activities, effects of radiation damage, hydrogen, helium and other transmutation impurities in materials, particle transport calculations, heavy liquid metal corrosion and compatibility, and materials engineering. The main progress, with an emphasis on materials technology in different projects, namely the US Spallation Neutron Source (SNS), the European Spallation Source (ESS), the Japanese Spallation Neutron Source (JSNS), the Swiss Spallation Neutron Source (SINQ) and the US Accelerator Production of Tritium facility (APT) was overviewed. Progress from the European TECLA and SPIRE programs was described. The achievements of investigations in the last two years on mechanical properties and microstructures of materials under high-energy proton (spallation), neutron and low energy ion irradiations were reported. The latest results from studies on corrosion and embrittlement effects of heavy liquid metals (Hg, Pb–Bi and Pb) were presented. Some critical issues of liquid metal technology related to accelerator driven systems (ADS), e.g. oxygen control and oxygen measurements were discussed.