[en] We calculate the chiral condensate < anti psipsi> for all quark masses using Kogut-Susskind fermions in lattice-regularized quenched QCD. The large volume behaviour of < anti psipsi> at small quark masses demonstrates that the explicit U(1) chiral symmetry is spontaneously broken. We perform the calculation for β = 5.1 to 5.9 and find very good continuum renormalization group behaviour. We infer that the spontaneous breaking we observe belongs to continuum QCD. This constitutes the first unambiguous demonstration of spontaneous chiral symmetry breaking in continuum quenched QCD. (orig.)