The diamagnetic susceptibility of two helium atoms is calculated as a function of atomic separation R and the spherical-average incremental susceptibility is evaluated. The Hartree-Fock approximation is used at intermediate separations and perturbation theory for the leading, 1/R-6, term in the increment at large separations. The change in average atomic susceptibility in liquid helium, relative to that for isolated atoms, is estimated. It is concluded that measurements on the liquid may be used to accurately determine the isolated atom diamagnetic susceptibility.