This paper provides a theoretical framework to understand the way in which exchange controls modify the behavior of the different agents in the economy, leading to the creation of a parallel market economy. It gives the necessary theoretical elements to analyze this parallel market economy and provides a simple methodology to obtain relevant quantitative information about it. Finally, the paper elaborates on some of the policy implications of the existence of a parallel market economy. The model developed shows that the parallel market activities can be explained through the optimizing behavior of exporters and importers, which determines the amount of import and export smuggling, the level of the rent-seeking activity, and the black market exchange rate that is consistent with an equilibrium position where no one has any more incentives to move from their attained position. A method to detect the presence, and assess the magnitude of the parallel market economy, as well as to explain its behavior quantitatively, is then developed and applied to the case of Ghana.