The theory of the ground state hyperfine splitting in hydrogen-like lead an
d lithium-like bismuth is discussed. A method for calculation of the Bohr-W
eisskopf correction in lithiumlike Bi, based on using the experimental resu
lt for the ground state hyperfine splitting in hydrogen-like Bi, is propose
d. The ground state hyperfine splitting in Bi-209(80+) is calculated to be
Delta E = 0.7969(2) eV.