High-frequency switching of single domain, uniaxial magnetic particles is discussed in terms of transition rates controlled by a small transverse bias field. It is shown that fast switching times can be achieved using bias fields an order of magnitude smaller than the effective anisotropy field. Analytical expressions for the switching time are derived in special cases, and general configurations of practical interest are examined using numerical simulations. (C) 1999 American Institute of Physics. [S0003-6951(99)00834-7].