2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/47422I review the status of theoretical aspects of B-decays. The principal difficulty in interpreting the wealth of experimental data is the control of non-perturbative QCD effects, and the talk is focused on attempts to control these effects. Lattice results for the decay constants, B-$\bar B$ mixing and semileptonic form-factors are summarized. The discrepancy of the theoretical predictions and experimental measurements for the ratio of lifetimes $τ(Λ_b)/τ(B_0)$ is discussed, as well as the status of the semileptonic branching ratio of the B-meson. The difficulties in making quantitative predictions for exclusive nonleptonic decays are stressed, and some recent approaches to this problem are outlined.Plenary lecture presented at the XVIII International Symposium on Lepton-Photon Interactions, Hamburg, July 28th - August 1st 1997. To be published in the Proceedings. 23 Pages - Latex file plus six *.eps figures and 2 style filesHigh Energy Physics - Phenomenologytext