AbstractData on the temperature dependence of viscosity obtained on three different polystyrenes with narrow molecular weight distributions are fitted to the Vogel, Fulcher, Tamman, and Hesse (VTFH) equation as well as to two intersecting Arrhenius lines. Both fits are optimized by means of computer programs. The data were chosen to fit the requirements stated by Boyer. The results of the analyses support the earlier conclusions that temperature‐dependent viscosity data do not indicate the presence of any liquid‐liquid transitionTLLabove the glass temperatureTg. In addition, evidence is presented which indicates that the viscosity atTgof high‐molecular‐weight polystyrenes is proportional to the 3.4 power of the molecular weight. HenceTgis not an isoviscous temp