  The anomalous dimensions of four-quark operators $(\bar q_i q_j)_{V-A} (\bar
q_k q_l)_{V-A}$ are calculated in the large $N_f$ limit. As expected, the
result is a convergent series without renormalon ambiguities. Using the
approximation of "Naive Nonabelianization", an additional all-order
contribution to the anomalous dimension matrix is obtained which is somewhat
larger than the exact NLO correction itself. Possible phenomenological
applications in nonleptonic B decays and $B^0 - \bar B^0$ mixing are briefly
considered.
