The author studies how well one can extrapolate the values of supersymmetry-breaking parameters to very high energy scales using future data from the Large Hadron Collider and an e(+)e(-) linear collider. He considers tests of the unification of squark and slepton masses in supergravity-inspired models. In gauge-mediated supersymmetry breaking models, he assesses the ability to measure the mass scales associated with supersymmetry breaking. He also shows that it is possible to get good constrains on a scalar cubic stop-stop-Higgs couplings near the high scale. Different assumptions with varying levels of optimism about the accuracy of input parameter measurements are made, and their impact on the extrapolated results is documented.