Can reparametrization invariance solve the cosmological constant problem?

The relevance of a dilaton field to the cosmological constant problem is examined from a macroscopic point of view. A special class of dilaton potentials is shown to possess an interesting reparametrization invariance, which might explain why the cosmological constant is so small. It is argued that, in a sense, this reparametrization invariance is an exact classical symmetry of superstrings. Simple dimensional arguments based on this scenario are shown to have interesting implications, including the prediction {\rho_{VAC}}\sim{\rho_C}