2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/49656I summarise the virtual effects of the new particles predicted by supersymmetric extensions of the Standard Model on the high-precision electroweak observables measured at LEP/SLC, the Tevatron and CLEO. I will then discuss in some details the two-loop SUSY-QCD corrections to the $ρ$ parameter.Latex, 18 pages, 6 figures, sprocl.sty included. Lecture given at X Escola de Particulas e Campos, Feb. 1999, Sao Paulo, BrazilHigh Energy Physics - Phenomenologytext