The extensional viscosity for aqueous solutions of high molecular weight poly(acrylamide) copolymers and poly(ethylene oxide) homopolymers was measured using a laboratory-designed screen extensional rheometer. A Bingham model was developed to estimate the average local polymer coil extensional viscosity (eta (coil)). A strong correlation was found between the measured eta (coil) values and the polymer extensional viscosity predicted by a bead-spring model. The dilute aqueous solution drag reduction was measured with a rotating disk instrument under conditions minimizing the effects of shear degradation. Extensional viscosity and drag reduction measurements were performed in deionized water and in 0.514M sodium chloride. The relative drag reduction efficiency values (A) in both solvents were found to strongly correlate with measured eta (coil), values. This is the first report of the accurate prediction of drag reduction behavior for a wide range of polymer types in various solvents from the independently measured molecular parameters eta (coil) and [eta ]C. The often-used relative drag reduction efficiency expressed as the product of [eta ]C and Delta can now be replaced by the absolute drag reduction efficiency