[en] We calculate the O(α_s²β₀) corrections to the decay rate b→c bar cs. For reasonable values of m_c/m_b this term is of the same order as both the one-loop and O(α_s²ln²m_W/m_b) corrections to the decay rate. For m_c/m_b=0.3 the O(α_s²β₀) corrections enhance the rate by ∼18% . We also discuss the O(α_s²β₀) corrections to b→cτ bar ν_τ, the B semileptonic branching fraction, and the charm multiplicity. copyright 1997 The American Physical Society