  We discuss numerical results of relativistic magnetohydrodynamic (MHD) jet
formation models. We first review some examples of stationary state solutions
treating the collimation and acceleration process of relativistic MHD jets. We
provide an a posteriori check for the MHD condition in highly magnetized flows,
namely the comparison of particle density to Goldreich-Julian density. Using
the jet dynamical parameters calculated from the MHD model we show the
rest-frame thermal X-ray spectra of the jet, from which we derive the overall
spectrum taking into account a variation of Doppler boosting and Doppler shift
of emission lines along the outflow. Finally, we present preliminary results of
relativistic MHD simulations of jet formation demonstrating the acceleration of
a low velocity (0.01c) disk wind to a collimated high velocity (0.8c).
