URL des Documents de travail : http://ces.univ-paris1.fr/cesdp/cesdp2015.htmlDocuments de travail du Centre d'Economie de la Sorbonne 2015.44R - ISSN : 1955-611X. Version originale Mai 2015, révisée en Décembre 2016, acceptée le 15 Décembre 2016 par Economic Theory.We consider a general equilibrium model of a private ownership economy with consumption and production externalities. The choices of all agents (households and firms) may affect utility functions and production technologies. The allocation of a competitive equilibrium is a Nash equilibrium. We provide an example showing that, under standard assumptions, competitive equilibria are indeterminate in an open set of the household's endowments. We introduce the model with firms' endowm...