With　the　ever-increasing　growth　of　data　and　information,　finding　the　right　knowledge　becomes　a　real　challenge　and　an　urgent　task.　Traditional　data　and　information　retrieval　systems　that　support　the　current　web　are　no　longer　adequate　for　knowledge　seeking　tasks.　Knowledge　retrieval　systems　will　be　the　next　generation　of　retrieval　system　serving　those　purposes.　Basic　issues　of　knowledge　retrieval　systems　are　examined　and　a　conceptual　framework　of　such　systems　is　proposed.　Theories　and　Technologies　such　as　theory　of　knowledge,　machine　learning　and　knowledge　discovery,　psychology,　logic　and　inference,　linguistics,　etc.　are　briefly　mentioned　for　the　implementation　of　knowledge　retrieval　systems.　Two　applications　of　knowledge　retrieval　in　rough　sets　and　biomedical　domains　are　presented.　©　2007　IEEE.