  Using a collapsar progenitor model of MacFadyen & Woosley we have simulated
the propagation of an axisymmetric jet through a collapsing rotating massive
star with the GENESIS multi-dimensional relativistic hydrodynamic code. The jet
forms as a consequence of an assumed (constant or variable) energy deposition
in the range $10^{50}$ erg s$^{-1}$ to $10^{51}$ erg s$^{-1}$ within a
$30^{\circ}$ cone around the rotation axis. The jet flow is strongly beamed
($\la$ few degrees), spatially inhomogeneous, and time dependent. The jet
reaches the surface of the stellar progenitor ($R_{\ast} = 2.98 \times 10^{10}
$cm) intact. At breakout the maximum Lorentz factor of the jet flow is 33.
After breakout the jet accelerates into the circumstellar medium, whose density
is assumed to decrease exponentially and then being constant $\rho_{\rm ext} =
10^{-5}$ gcm$^{-3}$. Outside the star the flow begins to expand also laterally
($v \sim c$), but the beam remains very well collimated. At a distance of $2.54
R_{\ast}$, where the simulation ends, the Lorentz factor has increased to 44.
