Neutrino mass texture with large mixing

We propose a simple texture for the right-handed Majorana mass matrix to give a large nu(mu)-nu(tau) mixing angle and hierarchical left-handed neutrino mass pattern. Consistently with the Dirac mass texture of the quark sector realizing the CKM I mixing, this naturally explains the recent experimental results on both the atmospheric neutrino anomaly observed by the Superkamiokande Collaboration and the solar neutrino problem. In this texture the right-handed Majorana mass of the third generation is of the order of grand unification theory scale, which is favorable for reproducing the observed bottom-tau mass ratio.