This book, i. e. , LNAI vol. 4223, is the proceedings of the Third International Conference on Fuzzy Systems and Knowledge Discovery (FSKD 2006), jointly held with the Second International Conference on Natural Computation (ICNC 2006, LNCS vols. 4221 and 4222) during September 24 – 28, 2006 in Xi’an, Shaanxi, China. FSKD 2006 successfully attracted 1274 submissions from 35 countries/regions(the joint ICNC-FSKD 2006received3189submissions). After rigorous reviews, 165 high-quality papers, i. e. , 115 long papers and 50 short papers,wereincludedintheFSKD2006proceedings,representinganacceptance rate of 13. 0%. ICNC-FSKD 2006 featured the most up-to-date research results in com- tational algorithms inspired from nature, including biological, ecological, and physical systems. It is an exciting and emerging interdisciplinary area in which a wide rangeof techniques and methods arebeing studied for dealing with large, complex, and dynamic problems. The joint conferences also promoted cro- fertilization over these exciting and yet closely related areas, which had a s- ni?cant impact on the advancement of these important technologies. Speci?c areas included neural computation, quantum computation, evolutionarycom- tation, DNA computation, fuzzy computation, granular computation, arti?cial life, etc. , with innovative applications to knowledge discovery, ?nance, ope- tions research, and more. In addition to the large number of submitted papers, we were honored with the presence of six renowned keynote speakers.