This book constitutes the refereed proceedings of the 21st International Symposium on Computer and Information Sciences, ISCIS 2006, held in Istanbul, Turkey in October 2006.

The 106 revised full papers presented together with 5 invited lectures were carefully reviewed and selected from 606 submissions. The papers are organized in topical sections on algorithms and theory, bioinformatics, computational intelligence, computer architecture, computer graphics, computer networks, computer vision, data mining, databases, embedded systems, information retrieval, mobile computing, parallel and distributed computing, performance evaluation, security and cryptography, as well as software engineering.