This book constitutes the refereed proceedings of the Third International Conference on Rough Sets and Knowledge Technology, RSKT 2008, held in Chengdu, China, in May 2008. The 91 revised full papers papers presented together with 3 keynote papers and 6 tutorial papers were carefully reviewed and selected from 184 submissions. They all focus on five major research fields: computing theory and paradigms, knowledge technology, intelligent information processing, intelligent control, and applications. The papers are organized in topical sections on rough and soft computing, rough mereology with applications, dominance-based rough set approach, fuzzy-rough hybridization, granular computing, logical and mathematical foundations, formal concept analysis, data mining, machine learning, intelligent information processing, bioinformatics and cognitive informatics, web intelligence, pattern recognition, and real-life applications of knowledge technology.