Intelligence and Security Informatics (ISI) is concerned with the study of the development and use of advanced information technologies and systems for national, international, and societal security-related applications. The annual IEEE International Conference series on ISI was started in 2003. In 2006, the Workshop on ISI (http://isi.se.cuhk.edu.hk/2006/) was started in Singapore in conjunction with the Pacific Asia Conference on Knowledge Discovery and Data Mining, with most contributors and participants from the Pacific Asian region. The Pacific Asia Workshop on Intelligence and Security Informatics was then held in Chengdu (http://isi.se.cuhk.edu.hk/2007/) in 2007.  These past ISI conferences have brought together academic researchers, law enforcement and intelligence experts, information technology consultant and practitioners to discuss their research and practice related to various ISI topics including ISI data management, data and text mining for ISI applications, terrorism informatics, deception and intent detection, terrorist and criminal social network analysis, public health and bio-security, crime analysis, cyber-infrastructure protection, transportation infrastructure security, policy studies and evaluation, information assurance, among others. We continue this stream of ISI conferences by organizing the 2008 Pacific Asia Workshop on ISI (PAISI 2008) in conjunction with IEEE International Conference on Intelligence and Security Informatics 2008.  PAISI 2008 will provide a stimulating forum for ISI researchers in Pacific Asia and other regions of the world to exchange ideas and report research progress. The workshop also welcomes contributions dealing with ISI challenges specific to the Pacific Asian region.