Atmospheric neutrino mixing and b–τ unification

Extrapolating the τ and b masses in the MSSM tends to give for their ratio at the GUT scale a number around 1.2, for most viable values tanβ, rather than the minimal SU(5) prediction of 1. We suggest that this may be due to large off-diagonal elements in the charged lepton mass matrix ML that can also explain the large atmospheric neutrino mixing angle. Several simple models with definite predictions for mτ/mb(MGUT) are presented.