Gyroviscous theory for the radial transport of toroidal momentum and the related theory for the poloidal variation of the angular rotation frequency in a Tokamak with strong rotation due to NBI are reviewed. Supporting theoretical and experimental evidence are cited. Stacey confirms that gyroviscosity can account for the momentum confinement times measured in Tokamak plasmas with directed NBI. A recent paper by Connor et al. (1987, ibid., vol.29, p.919, 1987) which arrived at a different conclusion and which criticized his theory is discussed.