Ciao, i works with Pharo 4.0 environment. I have a class Product with some instance variable and the = method set to: = anItem anItem ifNil:[^false]. anItem class = self class ifFalse:[ ^false]. ^ rfrConsegna = anItem rfrConsegna and:[ rfrSubTable = anItem rfrSubTable and:[ rfrDcm = anItem rfrDcm and:[ indexRiga = anItem indexRiga and:[ referenceTime = anItem referenceTime and:[ consumer = anItem consumer and:[ item = anItem item and:[ opzioniVoce = anItem opzioniVoce ]]]]]]] Some of these variables are instances of classes with specific implementation and some variables themselves. I set the relative hash method to: hash ^ rfrConsegna hash bitXor:( rfrSubTable hash bitXor: ( rfrDcm hash bitXor: ( indexRiga hash bitXor: ( referenceTime hash bitXor: ( consumer hash bitXor: ( item hash bitXor: ( opzioniVoce hash ))))))) Now when add some setup instances of class Product to a bag, the relative inspector report some aProduct entry but with some Occurences of this set to 0. aProduct1 3 aProduct2 0 aProduct3 0 Some consideration about it ? Some references about hash implementations ? Thanks, Dario