[en] I review experimental results on the reactions e⁺e^- -> e⁺e^-e⁺e^- and e⁺e^- -> e⁺e^-μ⁺μ^- from PETRA and PEP. Recent high statistics measurements are compared to QED predictions in the form of diagrammatic leading order (α₄) calculations and to the equivalent photon approximation. The leading order calculation describes the data well over the full kinematic range covered by experiments (0.1 < or approx. Q₂ < or approx. 100 GeV₂/c₂). The ''two photon interaction'' graph is found to saturate the observed cross section. Only for small masses of the produced leptonic system, first indications of a bremsstrahlung type background are observed at the percent level. The leptonic structure function F²sup(ß)(x, Q₂) is measured and also agrees with the behavior expected from QED. (orig.)