The two-dimensional subsonic cascade unsteady aerodynamic theory of Jones and Rao (1975) has been modified to account for the variable sweep angles of the blades of advanced turbopropellers. The aerodynamics and the structural modal properties have been formally integrated to determine the generalized aerodynamic coefficients matrix for the blade modes. Modal flutter analysis has been conducted for two SR-5 five- and ten-blade propellers, and analytical results have been found to be in very good agreement with wind tunnel test data.