We extend the standard “prices versus quantities” framework for pollution control to cover multiple heterogeneous jurisdictions interacting strategically with each other. When multi-jurisdictional externalities are present and the uncertainties among jurisdictions are independent, the regulatory game exhibits a unique subgame perfect equilibrium. For any one jurisdiction, the equilibrium choice of instrument is given by the sign of the original prices versus quantities formula. Thus, it is an optimal strategy for a jurisdiction to choose a price instrument when the slope of its own marginal benefit is less than the slope of its own marginal cost and a quantity instrument when this condition is reversed. The result suggests that the original nonstrategic criterion for the comparative advantage of prices over quantities may have wider applicability to determining instrument choice in a noncooperative strategic environment.