Precision tests of the Electroweak interactions at e+e- collisions

This paper is an updated version of the lectures given at the XXIX International Meeting on Fundamental Physics in Sitges, Barcelona (February 2000). The measurements perforned at LEP and SLC have substantially improved the precision of the test of the Minimal Standard Model. The precision is such that there is sensitivity to pure weak radiative corrections. This allows to indirectly determine the top mass (m_t = 180 +- 10GeV), the W-boson mass (M_W = 80.375 +- 0.022GeV), and to set an upper limit on the Higgs boson mass of 196GeV at 95% confidence level.