  We show that for long-baseline experiments using a Mt water Cerenkov detector
atmospheric neutrino data provide a powerful method to resolve parameter
degeneracies. In particular, the combination of long-baseline and atmospheric
data increases significantly the sensitivity to the neutrino mass hierarchy and
the octant of $\theta_{23}$. Furthermore, we discuss the possibility to use
$\mu$-like atmospheric neutrino data from a big magnetized iron calorimeter to
determine the neutrino mass hierarchy.
