The time-dependent parallel viscosity (B. Del Pi a) is calculated in an axisymmetric toroidal plasma with arbitrary aspect ratio. By using this parallel viscosity, the relaxation rate nu p of the poloidal rotation in Tokamak plasmas is obtained in the banana regime. The analytical fit for this relaxation rate is also computed. In large-aspect-ratio Tokamaks, this relaxation rate nu p is found to be of the order nu ii square root epsilon and the previously-derived result nu p approximately nu ii by Shaing et al. (1989) is shown to be incorrect, where nu ii and epsilon are the ion-ion collision frequency and the inverse aspect ratio.