Self-consistent nonlinear changes of plasma parameters and characteris
tics of electromagnetic guided waves are studied with regard to the ef
fect of self-focusing and waveguided channel formation in a cylindrica
l plasma waveguide. Besides the nonlinearity due to the ponderomotive
force action usually involved, ionization nonlinearity specified for d
ifferent regimes of particle loss mechanisms is considered. An azimuth
ally symmetric electromagnetic surface wave is the guided mode that fo
rms and sustains the wave channel. The nonlinear dispersion law and th
e nonlinear changes in the wave field distribution and power flow are
obtained, describing the effect of the self-focusing of the wares unde
r conditions of weak nonlinearity.