In this paper we analyze a basic sticky price model with monopolistic competition and price stickiness à la Calvo. Starting by the relations de- scribing a general economic equilibrium model (see Woodford in Interest and Prices, Foundations of a Theory of Monetary Policy, The MIT Press, 2003), as it results from the optimizing behavior of the private agents, we provide a nonlinear model for the monetary policy analysis. This kind of model is a candidate for the existence of multiple equilibria, with a de- pendence of exogenous sunspots. We explore the stability of such a model combined with interest rate rules in order to investigate the determinacy of the model and we nd, for some policy and elasticity parameters, the conditions...