Since I don't have any evidence of what happened I will have to guess: This looks like a recursive write. Are you trying to use HashMaps as trees? A recursive write is okay, but if you keep adding circular references you won't have stack to process the recursive calls necessary here. Something like: Map.put(key, AnotherMap); AnotherMap.put(key,SubMap); Maybe indirectly through fields? Or maybe your code has some loop doing that by accident? If you ask for my guess, I would say this is the most possible cause. If this is not true, What operation where you performing. Is this using any POJOs you wrote? Maybe there is something wrong with them? On any case this is a symptom of another bug, and I don't think this is a bug on the Serialization itself. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4165063#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...