We compute the matrix elements of the operators which contribute to sp
ectator effects in inclusive decays of B-mesons. The results agree wel
l with estimates based on the vacuum saturation (factorization) hypoth
esis. For the ratio of lifetimes of charged and neutral mesons we find
tau(B-)/tau(B-d) = 1.03 +/- 0.02 +/- 0.03, where the first error repr
esents the uncertainty in our evaluation of the matrix elements, and t
he second is an estimate of the uncertainty due to the fact that the W
ilson coefficient functions have only been evaluated at tree-level in
perturbation theory. This result is in agreement with the experimental
measurement. We also discuss the implications of our results for the
semileptonic branching ratio and the charm yield. (C) 1998 Elsevier Sc
ience B.V.