Discrepancies arise among magnitudes as derived from local earthquake data (ML), body waves (MB) and surface waves (MS). The relation of ML to the others is as yet not definitive; but MS – mB = a (MS – b). The latest revision gives a = 0.37, b = 6.76. Pending further research it is recommended that ML continue to be used as heretofore, but MS (and ultimately ML) should be referred to mB as a general standard, called the unified magnitude and denoted by m. Tentatively log E = 5.8 + 2.4 m (E in ergs). Revised tables and charts for determining m are given.