The effect of molecular weight on the rheological properties in the molten state has been studied for binary blends of high-density polyethylene obtained by the Zieglar-Natta catalyst and low-density polyethylene produced in an autoclave process. The blends composed of high-density polyethylene with a high molecular weight and low-density polyethylene show a higher drawdown force than the individual pure components, whereas the blends of high-density polyethylene with a low molecular weight and low-density polyethylene do not exhibit anomalous behavior. The pronounced drawdown force for the former blend system is attributed to the viscous enhancement in the linear viscoelastic region as well as the nonlinear strain-hardening behavior in the elongational viscosity.