  We present an implementation of the next-to-leading order hadronic production
of a W boson in association with a pair of massive bottom quarks in the
framework of POWHEG, a method to consistently interface NLO QCD calculations
with shower Monte Carlo generators. The process has been implemented using the
POWHEG BOX, an automated computer code that sistematically applies the POWHEG
method to NLO QCD calculations. Spin correlations in the decay of the W boson
into leptons have been taken into account using standard approximated
techniques. We present phenomenological results for W b bbar-> l nu b bbar
production, at both the Tevatron and the LHC, obtained by showering the POWHEG
results with PYTHIA and HERWIG, and we discuss the outputs of the two different
shower Monte Carlo programs.
