This　paper　discusses　a　knowledge　system　for　organisational　decision　making　on　waste　elimination　to　achieve　lean　production.　The　system　is　named　Production　Waste　Elimination　Knowledge　System　(ProWEKS).　An　empirical　study　was　undertaken　to　obtain　production　engineers　and　managers＇　empirical　knowledge　and　expertise.　A　knowledge　acquisition　matrix　has　been　designed　for　the　knowledge　elicitation　activity.　A　waste　elimination　knowledge　model　is　proposed　which　captures　the　inter-relationships　between　different　knowledge　components　across　four　knowledge　layers　including　know-what,　know-how,　know-why　and　know-with.　A　knowledge　base　has　been　developed　based　on　the　knowledge　model　through　constructing　a　decision　tree.　The　system　is　demonstrated　and　evaluated　using　a　quality　control　decision　case　from　the　electronics　industry.　The　main　contribution　of　the　paper　is　that　it　proposes　a　new　knowledge　architecture　which　comprehensively　captures　not　only　the　know-what　and　know-how,　but　also　the　know-why　and　know-with　of　the　waste　elimination　knowledge　for　lean　production.　©　2012　Springer-Verlag.