  A study of the charmless semileptonic decay B0 to pi- l+ nu using a large
sample of untagged Upsilon(4S) to B Bbar events collected with the Belle
detector at the KEKB asymmetric e+ e- collider is presented. The branching
fraction of the decay is obtained and from this the Cabibbo-Kobayashi-Maskawa
matrix element |Vub| is determined using two different approaches.
