  Using the Monte Carlo simulations we apply a method of discrete small
amplitude particle momentum scattering to reproduce highly anisotropic
conditions at relativistic shocks. We discusse acceleration times scales in
relativistic shocks. Next, we describe newly found acceleration mechanism at
ultrarelativistic shocks. The universal spectral index and the acceleration
time for the shocks are given. In the end reflections from ultrarelativistic
shocks are considered.
