[en] We assess the possibility of measuring the trilinear self-coupling of the standard model Higgs boson at future electron-positron linear colliders with centre-of-mass energies between 500 and 1500 GeV. We consider rather light Higgs scalars, with mass below the W⁺W^- threshold, produced in the double Higgs-strahlung channel e⁺e^-→HHZ and decaying via the dominant mode H→b anti b. Assuming ideal vertex tagging of the heavy-quark jets and mass reconstruction of the Z boson produced in association with the Higgs pair, we compare the yield of the above process to those of all irreducible electroweak and strong backgrounds proceeding through a b anti bb anti bZ intermediate state. Total cross sections and differential spectra of phenomenological relevance to the selection and analysis of the signal are given and discussed. (orig.)