HEAVY-TO-LIGHT MESON TRANSITIONS IN QCD

I discuss QCD sum rules determinations of the form factors governing t he decay B --> pi(rho)l nu. For some of these form factors the compute d dependence on the momentum transferred does not agree with the expec tation from the nearest pole dominance hypothesis. Relations are obser ved among the form factors, that seem to be compatible with equations recently derived by Stech. The measurement of a number of colour-suppr essed non-leptonic B decay rates could shed light on the accuracy of t he calculation of these form factors and on the factorization approxim ation.