Recent isotopic studies have suggested that the trace gas N2O has a missing stratospheric sink of potentially major significance. While these studies have raised interesting questions, the constraints on N2O photochemistry imposed by correlations between N2O, total reactive nitrogen, and other tracers measured in situ in the lower stratosphere also should be considered. Measured tracer correlations, when compared to the results of models using standard photochemistry, provide evidence in support of conventional N2O sinks. Stratospheric tracer correlations, however, cannot be used to preclude a new atmospheric source of N2O in the troposphere or to argue against an undiscovered stratospheric sink that contributes less than ~20% of the total sink. ¿ 1999 American Geophysical Union