  We report a measurement of the production ratio of charged and neutral B
mesons from Upsilon(4S) decays based on the ratio of efficiency-corrected
yields for the charmonium modes J/psi K^+ and J/psi K^{0}_{S} with 81.9 fb^-1
of data collected with the BABAR detector on the Upsilon(4S) resonance at
10.580 GeV. We find a value of 1.006 +/- 0.036 (stat) +/- 0.031 (sys) for the
ratio R^{+/0}=Gamma(Upsilon(4S) -> B^+ B^-)/Gamma(Upsilon(4S)->B^0 B^0bar).
