  We present a microscopic theory of spin-orbit coupling in the integer quantum
Hall regime. The spin-orbit scattering length is evaluated in the limit of
long-range random potential. The spin-flip rate is shown to be determined by
rare fluctuations of anomalously high electric field. A mechanism of strong
spin-orbit scattering associated with exchange-induced spontaneous
spin-polarization is suggested. Scaling of the spin-splitting of the
delocalization transition with the strength of spin-orbit and exchange
interactions is also discussed.
