  Propagation of radio emission in pulsar magnetosphere is reviewed. The
effects of polarization transfer, induced scattering and reprocessing to high
energies are analysed with an especial emphasis on the implications for the
gamma-ray pulsars. The possibilities of the pulsar plasma diagnostics based on
the observed radio pulse characteristics are outlined as well. As an example,
the plasma number density profiles obtained from the polarization data for the
Vela and the gamma-ray millisecond pulsars J1446-4701, J1939+2134 and
J1744-1134 are presented. The number densities derived tend to be the
highest/lowest when the radio pulse leads/lags the gamma-ray peak. In the PSR
J1939+2134, the plasma density profiles for the main pulse and interpulse
appear to fit exactly the same curve, testifying to the origin of both radio
components above the same magnetic pole and their propagation through the same
plasma flow in opposite directions. The millisecond radio pulse components
exhibiting flat position angle curves are suggested to result from the induced
scattering of the main pulse by the same particles that generate gamma-rays.
This is believed to underlie the wide-sense radio/gamma-ray correlation in the
millisecond pulsars. The radio quietness of young gamma-ray pulsars is
attributed to resonant absorption, whereas the radio loudness to the radio beam
escape through the periphery of the open field line tube.
