Semileptonic decays of heavy-light pseudoscalar mesons

I discuss the results of a recent quenched lattice calculation of the two independent form factors parametrizing the semileptonic decays between heavy-light pseudoscalar mesons. The differential decay rate of the process B –> D l nu has been calculated at non vanishing momentum transfer both in the case of the light leptons, l=e,mu, and in the case of a non vanishing lepton mass, l=tau.