The P.I. has developed a finite difference model that describes the evolution of stretching and rifting along passive continental margins. Funding has been granted for the P.I. to reconcile his theoretical studies with observational data from the margins of the U.S. east cost and Red Sea. An attempt will be made to account for the asymmetric nature of rifting, the shifting of the locus of maximum extension with time, and the distribution of uplift and magmatism prior to and during rifting. This model needs no a apriori assumptions regarding the character of shearing as either "simple" or "pure", acommon starting point that limits other modeling techniques in their ability to duplicate the variety of features that typify rifted margins.