Résumé : In a sample of 38238 interactions found in photographic emulsions exposed to K- mesons of 1.3 and 1.5 GeV/c momenta, a total of 1385 heavy hypernuclei (40 < A < 100) were observed, of which 11 decayed mesonically. The following results were obtained: an upper limit of 27±3 MeV for the Λ0 nuclear potential well depth, a value of Q- in the range 100 to 200 and a fraction, n, in the range 0.6 to 0.9 of non-mesonic decays stimulated by the weak Λ0-neutron interaction. © 1964.