The apparent uniaxial extensional viscosity or elongational viscosity,ηE,of several polymer melts in a wide range of temperatures was determined as a function of strain rate, ε̇, using Cogswell's analysis of converging flow at the die entry. In particular,ηEwas derived from knowledge of the dependence of the steady‐flow viscosity as well as the entrance pressure drop,δP0,on shear rate. Quantitative agreement was found inηE−ε̇dependence derived from the convergent flow analysis (CFA) along with that measured from isothermal melt-spinning experiments for melts of high‐density and low‐density polyethylene, polypropylene, and polystyrene. Further support of CFA comes from the finding here that the normalized entrance pressure drop,δP0/τ,is uniquely related to the vortex angle in a manner similar to that determined from flow visualization studies by Ballenger and White. Here τ is the shear stress at the die wall. Additionally, the flow activation energy in extension is found to be equal to that in shear for melts of low‐density polyethylene, polypropylene, and polystyrene. Such observations are in line with the earlier results of Munsted on polystyrene melts. An anomaly exists for high‐density polyethylenes sinceηEincreased with increases in temperature above a critical temperature. Finally, the shapes of extensional flow curves are found to be similar to the published data, although an exception such as low‐melt‐index, low‐density polyethylene, whereηEdecreases with ε̇, is cited.