  We describe the implementation of top production and decay processes in the
parton-level Monte Carlo program MCFM. By treating the top quark as being
on-shell, we can factorize the amplitudes for top-pair production, s-channel
single-top production, and t-channel single-top production into the product of
an amplitude for production and an amplitude for decay. In this way we can
retain all spin correlations. Both the production and the decay amplitudes are
calculated consistently at next-to-leading order in alpha_s. The full
dependence on the b-quark mass is also kept. Phenomenological results are
presented for various kinematic distributions at the LHC and for the top quark
forward-backward asymmetry at the Tevatron.
