If there's any relationship between the entities in Jar1 and Jar2 (associations, mapped superclasses, etc), you'll have to reference the classes in Jar1's persistence.xml file under the "class" node: DTD: <!ELEMENT persistence (persistence-unit*)> | <!ELEMENT persistence-unit (description?,provider?,jta-datasource?, | non-jta-datasource?,(class|jar-file|mapping-file)*, | exclude-unlisted-classes?,properties?)> | <!ATTLIST persistence-unit name CDATA #REQUIRED> | <!ATTLIST persistence-unit transaction-type (JTA|RESOURCE_LOCAL) "JTA"> | <!ELEMENT description (#PCDATA)> | <!ELEMENT provider (#PCDATA)> | <!ELEMENT jta-datasource (#PCDATA)> | <!ELEMENT non-jta-datasource (#PCDATA)> | <!ELEMENT mapping-file (#PCDATA)> | <!ELEMENT jar-file (#PCDATA)> | <!ELEMENT class (#PCDATA)> | <!ELEMENT exclude-unlisted-classes EMPTY> | <!ELEMENT properties (property*)> | <!ELEMENT property EMPTY> | <!ATTLIST property name CDATA #REQUIRED> | <!ATTLIST property value CDATA #REQUIRED> View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4088630#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...