  We argue that the B^0 B^0 bar state generated in the decay of Upsilon(4S) is
well suited for performing tests of Einstein-Podolsky-Rosen correlations, i.e.,
quantum-mechanical interference effects over macroscopic distances. Using
measurements of the ratio R = (#like-sign dilepton events)/(#opposite-sign
dilepton events) and of the B_H - B_L mass difference we show that already
presently existing data strongly favour the contribution of the interference
term to R, as it is required by the rules of quantum mechanics.
