Minimal supersymmetric standard model and large tan beta from SUSY trinification.

We construct a supersymmetric model based on the semisimple gauge group SU(3)[sub [ital c]][times]SU(3)[sub [ital L]][times]SU(3)[sub [ital R]] with the relation tan[beta][congruent][ital m][sub [ital t]]/[ital m][sub [ital b]] automatically arising from its structure. The model below a scale [similar to]10[sup 16] GeV naturally gives rise just to the minimal supersymmetric standard model and therefore to the presently favored values for sin[sup 2][theta][sub [ital W]] and [alpha][sub [ital s]] without fields in representations higher than the fundamental.