[en] Elastic scattering of 1.5 to 4.0 MeV neutrons from radiogenic lead, Pb sub (r), and ²⁰⁹Bi has been measured using a time-of-flight technique. The experimental results show the existence of a b broad maximun in the angle integrated elastic cross section centered at a neutron energy of about 3 MeV for both elements. Further, this cross-section maximum is more pronounced for ²⁰⁹Bi than for Pb sub (r). The data were analysed in terms of an optical model potential with spherical symmetry. The energy dependence of the total shape elastic cross sections calculated for Pb sub (r) and ²⁰⁹Bi from this model shows only minor differences, which are caused by the small mass difference and the fact that nuclear structure effects are not taken into account in the optical model. The observed cross section differences between Pb sub (r) and ²⁰⁹Bi have been explained as a compound nucleus effect caused by the essentially larger ground state spin of ²⁰⁹Bi as compared to Pb sub (r). Different formalisms have been used to correct the calculated compound elastic cross sections for level width fluctuations. (Author)