Guiding-center simulations of stormtime transport of ring-current and radiation-belt ions having first adiabatic invariants &mgr;>15 MeV/G (E>165 keV at L~3) are surprisingly well described (typically within a factor of ≲4) by the quasilinear theory of radial diffusion. This holds even for the case of an individual model storm characterized by substorm-associated impulses in the convection electric field, provided that the actual spectrum of the electric field is incorporated in the quasilinear diffusion coefficient DLLql for drift-resonance broadening (so as to define DLLrb) reduced the typical discrepancy with the diffusion coefficients DLLsim deduced from guiding-center simulations of representative-particle trajectories to a factor ~3. The typical discrepancy was reduced to a factor ~1.4 by averaging DLLsim, DLLql, and DLLrb over an ensemble of model storms characterized by different (but statistically equivalent) sets of substorm-onset times. ¿ American Geophysical Union 1992