  We use aMC@NLO to study the production of four charged leptons at the LHC,
performing parton showers with both HERWIG and Pythia6. Our underlying matrix
element calculation features the full next-to-leading order $O(\alpha_S)$
result and the $O(\alpha_S^2)$ contribution of the $gg$ channel, and it
includes all off-shell, spin-correlation, virtual-photon-exchange, and
interference effects. We present several key distributions together with the
corresponding theoretical uncertainties. These are obtained through a
process-independent technique that allows aMC@NLO to compute scale and PDF
uncertainties in a fully automated way and at no extra CPU-time cost
