Hi, I've writte a very simple product which creates 100 simple objects (testProd class instances) and each of these objects has a list-attribute which contains 200 other objects (item class instances). (Please find the code at the end of this mail.) By starting the addTestProd-function I create 20000 references to item objects, as the Zope-debug option as well as the leakFinder-product tell me. But I'll never get rid of these references and earlier or later I'll run out of memory. Could anybody explain me, way this simple product is leaking like a sieve? And how I can get rid of the references? thanks for your help in advance, Christoph here is the code: __init__.py: import testProd2 def initialize(context): """ initialize this product """ context.registerClass( testProd2.testProd, permission = 'Add testProd', constructors=(testProd2.addTestProd,)) testProd2.py: import OFS.SimpleItem as SimpleItem from OFS.SimpleItem import Item def addTestProd(self): """ add TestProd """ for c in range(100): name = 'test' + str(c) self._setObject(name, testProd(name)) class testProd(SimpleItem.SimpleItem): """ testProd docu """ meta_type = 'testProd' def __init__(self, id, title = ''): self.id = id self.title = title self._tree = [] for i in xrange(200): n = item(str(i),i) tree = self._tree tree.append(n) self._tree = tree class item(Item): """ item """ def __init__(self, id, value): self.id = id self.value = value