Implications of non-universality of soft terms in supersymmetric grand unified theories

Most discussions of supersymmetric grand unified theories assume universality of the soft supersymmetry breaking terms at the grand scale. We point out that the behaviour of these theories might change significantly in the presence of non--universal soft terms. Particularly in SO(10)--like models with a large value of tan$\beta$ we observe a decisive change of predictions, allowing the presence of relatively light gauginos as well as small supersymmetric corrections to the b--quark mass. Some results remain rather stable, including the $\mu$--$M_{1/2}$ correlation. Models with small tan$\beta$ seem to be less affected by non--universality which mainly leads to the new possibility of small $m_{0}$ (i.e. the squark and slepton soft mass parameter), excluded in the universal case.