Implications of the CERN LEP results for SO(10) grand unification

We consider the breaking of the grand unification group SO(10) to the standard model gauge group through several chains containing one intermediate breaking scale. Using the values of the gauge coupling constants at the scale $M_Z$ derived from recent data from the CERN $e^{+}{e}^{-}$ collider LEP, we determine the intermediate and the unification scales using two-loop renormalization group equations with appropriate matching conditions. Some chains are ruled out from experimental constraints. For the allowed ones, the intermediate scale is high, in the range of ${10}^9$ ${-10\mathrm{}}^{11}$ GeV.