  The ground state hyperfine splitting values of high Z hydrogenlike ions are
calculated. The relativistic, nuclear and QED corrections are taken into
account. The nuclear magnetization distribution correction (the Bohr-Weisskopf
effect) is evaluated within the single particle model with the g_{S}-factor
chosen to yield the observed nuclear moment. An additional contribution caused
by the nuclear spin-orbit interaction is included in the calculation of the
Bohr-Weisskopf effect. It is found that the theoretical value of the wavelength
of the transition between the hyperfine splitting components in ^{165}Ho^{66+}
is in good agreement with experiment.
