Determination of Vub at the Z-boson resonance

We show that the observation of energetic charged leptons from semileptonic b decays at the LEP and SLC Z-boson factories offers a unique opportunity to measure the quark mixing matrix element Vub. We present various distributions of the b decay products to show that the b → u decays can be cleanly separated from the b → c decays, with a signal of O(100) events per million Z bosons produced.