  We study the range of the elements of the neutrino mass matrix m_nu in the
charged lepton basis. Neutrino-less double beta decay is sensitive to the ee
element of m_nu. We then analyze the phenomenological implications of single
texture zeros. In particular, interesting predictions for the effective mass
can be obtained, in the sense that typically only little cancellation due to
the Majorana phases is expected. Some cases imply constraints on the
atmospheric neutrino mixing angle.
