We present a measurement of the time-dependent asymmetry in the
rate for B-bar^0_d versus B^0_d decays to J/psi K^0_S.  In the context of the
Standard Model this is interpreted as a measurement of the CP-violation
parameter sin(2B).  A total of 198 +/- 17 B^0_d/B-bar^0_d decays were observed
in ppbar collisions at sqrt s = 1.8 TeV by the CDF detector at the Fermilab
Tevatron.  The initial b-flavor is determined by a same side flavor tagging
technique.  Our analysis results in sin(2B) = 1.8 +/- 1.1(stat) +/- 0.3(syst).