The most promising ways to measure V_ub

I review currently discussed methods to determine the CKM mixing matrix element $\mathrm{\mid }{V}_{ub}\mathrm{\mid }$ from experimental data. Although the theory of inclusive decays and their spectra has entered a model-independent stage, its predictions are still sensitive to various input parameters, in particular the poorly known $b$ quark mass. At present, determinations from exclusive channels, notably $B\to \pi e\nu$, seem slightly more accurate and allow determination of $\mathrm{\mid }{V}_{ub}\mathrm{\mid }$ from the spectrum in the momentum transfer to the leptons with a theoretical uncertainty of $\sim 10$.