2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/148907We show in a simple and general way that MSW resonant transitions for solar neutrinos are not observable in the case of maximal mixing among any number of neutrino generations.RevTeX file, 4 pages. The postscript file is available at http://www.to.infn.it/teorici/giunti/papers.html Two misprints in Eq.(8) are correctedHigh Energy Physics - Phenomenologytext