The Third International Symposium on Large Spatial Databases (SSD '93) was held at the National University of Singapore in June 1993. The previous meetings of the series were at Sanata Barbara (1989) and Zurich (1991). The meetings are planned as a forum for researchers and practitioners specializing in database theory for and advanced applications of Spatial Information Systems. This volume constitutes the proceedings of the symposium. It contains 25 selected papersand three keynotes papers: "Spatial data management in database systems: research directions" (W. Kim), "From extensible databases to interoperability between multiple databases and GIS applications" (H.-J. Schek), and "The SEQUOIA 2000 project" (M. Stonebraker). The selectedpapers are collected into sections on: data modeling, spatial indexing, indexing mechanisms, handling of raster and vector data, spatial database systems, topology, storage management, query retrieval,knowledge engineering in SDS, and 3-dimensional data handling.