This Letter describes a measurement of the muon cross section originating f
rom b-quark decay in the forward rapidity range 2.4 < \y(mu)\ < 3.2 in p (p
) over bar collisions at root s = 1.8 TeV. The data used in this analysis w
ere collected by the DO experiment at the Fermilab Tevatron. We find that n
ext-to-leading-order QCD calculations underestimate b-quark production by a
factor of 4 in the forward rapidity region.