The usual demonstration that neoclassical transport is automatically ambipolar, and independent of the radial electric field (Er), is shown to be valid only in an equilibrium axisymmetric plasma in which there is no other source or damping of toroidal momentum. If it were generally true, it would be difficult to explain the measured current drawn from a biased internal probe, as used to induce H modes. However, this current and its variation with applied voltage are consistent with the alternative analysis by Galeev and Sagdeev (1968), in which the ion and electron fluxes depend on Er - BθŪ||. The behaviour of Er and impurity pump-out during enhanced MHD activity can also be explained using this analysis