which wa~ suggested by ZICmCHI et a l . (1). The experiment was carried out at 2.5 GcV/c incident antiproton momentum, which corresponds to a timelike fourmomentum transfer of 6.8 (GeV[e) 2. ~Ihe choice of this q2-value was dictated, by the requirement of the maximum number of observable events predicted, using the knowledge of the p flux as a function of momentum at the CERN PS, together with the behaviour of the cross-section as a function of the ~ momentum for processes (1) and. (2), which was calculated, assuming that the proton-photon interaction is pointlike. The aim of the experiment was twofold.: firstly, to measure the electromagnetic form factors for timclike four-momentum transfers and secondly to check the equivalence of the electromagnetic interactions of the electron and. the muon for timelike four-momentum transfers. In practice the cross-section was shown to be so low that only an upper l imit for annihilation into lepton pairs of