This book constitutes the refereed proceedings of the 20th International Conference on Scientific and Statistical Database Management, SSDBM 2008, held in Hong Kong, China, in July 2008. The 28 revised full papers, 7 revised short papers and 8 poster and demo papers presented together with 3 invited talks were carefully reviewed and selected from 84 submissions. The papers are organized in topical sections on query optimization in scientific databases, privacy, searching and mining graphs, data streams, scientific database applications, advanced indexing methods, data mining, as well as advanced queries and uncertain data.