This paper analyzes a regulation game with asymmetric information and lack of commitment. It expands Besanko and Spulber's (1989) framework to the case of elastic demands using a generalized Nash solution. It is found that the most important property of the equilibrium with inelastic demand is not carried over to the elastic demand case, i.e., incomplete information worsens underinvestment, contrasting to Besanko and Spulber's result.Facultad de Ciencias Económicas