We report a measurement of the fraction of b quarks produced diffractively
in (p) over bar p collisions at root s = 1.8 TeV. Diffraction is identified
by the absence of particles in a forward pseudorapidity region. From event
s with an electron of transverse momentum 9.5 < p(T)(e) < 20 GeV/c within t
he pseudorapidity region \eta\ < 1.1, the ratio of diffractive to total b-q
uark production rates is found to be R-(b) over bar b = [0.62 +/- 0.19(stat
) +/- 0.16(syst)]%. This result is comparable in magnitude to corresponding
ratios for W and dijet production but significantly lower than expectation
s based on factorization.