Résumé
We perform a comprehensive analysis of the decays of charginos andneutralinos in the Minimal Supersymmetric Standard Model where the neutralino$\chi_1^0$ is assumed to be the lightest supersymmetric particle. We focus, inparticular, on the three-body decays of the next-to-lightest neutralino and thelightest chargino into the lightest neutralino and fermion-antifermion pairsand include vector boson, Higgs boson and sfermion exchange diagrams, where inthe latter contribution the full mixing in the third generation is included.The radiative corrections to the heavy fermion and SUSY particle masses will bealso taken into account. We present complete analytical formulae for the Dalitzdensities and the integrated partial decay widths in the massless fermion case,as well as the expressions of the differential decay widths including themasses of the final fermions and the polarization of the decaying charginos andneutralinos. We then discuss these decay modes, in particular in scenarioswhere the parameter $\tan \beta$ is large and in models without universalgaugino masses at the Grand Unification scale where some new decay channels,such as decays into gluinos and $q\bar{q}$ pairs, open up.