It is our great pleasure to introduce the papers of the proceedings of the 9th - ternational Symposium on Spatial and Temporal Databases - SSTD 2005. This year’s symposium continues the tradition of being the premier forum for the presentation of research results and experience reports on leading edge issues of spatialandtemporaldatabasesystems, including data models,systems,appli- tions and theory. The mission of the symposium is to share innovative solutions that ful?ll the needs of novel applications and heterogeneous environments and identify new directions for future research and development. SSTD 2005 gives researchers and practitioners a unique opportunity to share their perspectives with others interested in the various aspects of database systems for managing spatial and temporal data and for supporting their applications. A total of 77 papers were submitted this year from several countries. After a thorough review process, the program committee accepted 24 papers covering a variety of topics, including indexing techniques and query processing, mobile environments and moving objects, and spatial and temporal data streams. We are very pleased with the variety of the symposium’s topics, and we are proud of the resulting strong program.