  In the light of the gathering evidence for $\nu_{\mu}-\nu_{\tau}$ neutrino
oscillations, coming in particular from the Super-Kamiokande data on
atmospheric neutrinos, we re-analyze the unification of gauge and Yukawa
couplings within the minimal supersymmetric extension of the Standard Model
(MSSM). Guided by a range of different grand-unified models, we stress the
relevance of large mixing in the lepton sector for the question of bottom-tau
Yukawa coupling unification. We also discuss the dependence of the favoured
value of $\tan\beta$ on the characteristics of the high-energy quark and lepton
mass matrices. In particular, we find that, in the presence of large lepton
mixing, Yukawa unification can be achieved for intermediate values of
$\tan\beta$ that were previously disfavoured. The renormalization-group
sensitivity to the structures of different mass matrices may enable Yukawa
unification to serve as a useful probe of GUT models.
