MSSM FROM SUSY TRINIFICATION

We construct a SU(3)3 supersymmetric gauge theory with a common gauge coupling g using only fields belonging to 27, 27BAR and singlet repres entations of E6. Spontaneous breaking of this gauge group at a scale M (x) = 1.3 x 10(16) GeV gives naturally rise exactly to the minimal sup ersymmetric standard model (MSSM) and, consequently, to the experiment ally favored values of sin2theta(w) and alpha(s). The gauge hierarchy problem is naturally solved by a missing-partner-type mechanism which works to all orders in the superpotential. The baryon asymmetry can be generated in spite of the (essential) stability of the proton. The so lar neutrino puzzle is solved by the MSW mechanism. The LSP is a natur al ''cold'' dark matter candidate and ''hot'' dark matter might consis t of tau-neutrinos. This model could be thought of as an effective 4D theory emerging from a more fundamental theory at a scale M(c) = M(p)/ square-root8pi where a(G) = g2/4pi happens to be equal to unity.