Nonperturbative QCD Effects in Inclusive B Decays

In this talk I report calculable nonperturbative QCD effects to the inclusive semileptonic and radiative B-meson decay rates. Small instantons contribute to the Wilson coefficient functions at scales below $m_b$. It is found that the instantons give rise to a potentially large correction to the decay rate near the boundaries of the phase space for the semileptonic decay case, but totally negligible for the radiative case. I explain how the difference may be understood as a simple consequence of different kinematics in the two cases. {Talk Presented at IFT Workshop on Yukawa Couplings and the Origin of Mass University of Florida, Gainesville, Feb. 11-13, 1994 Proceeding to be Published by International Press, 15 pages (LATEX) 5 Postscript figures available upon request, International Press macro file ip-author.sty appended}