  We investigate the spectrum of supersymmetric grand unification models based
on the gauge groups SU(5), SO(10) and E6, paying particular attention to the
first and second generation. We demonstrate how the measurement of the first or
second generation sfermion spectrum may be used to constrain the underlying
grand unification structure. The smallness of first and second generation
Yukawa interactions allows us to perform an analytic analysis, deriving
expressions for the high scale parameters in terms of the low scale sfermion
masses. We also describe a sum rule that provides an SO(10) mass prediction,
distinct from SU(5), and discuss E6 models, both with and without extra exotic
matter at low energies. The derived relations are compared with numerical
results including two-loop running and the full Yukawa dependence.
