The lifetime of the B(s)0 has been measured in a data sample of 889 00
0 hadronic events recorded with the ALEPH detector at LEP. After backg
round subtraction 30.8 +/- 6.9 events are attributed to the semilepton
ic decay of the B(S)0 to a D(S)- and an opposite-sign lepton. A maximu
m-likelihood fit to the distribution of the proper times of these even
ts yields a B(s)0 lifetime of tau(B)s = 1.92 (-0.35)+0.45 +/- 0.04 ps.