  Dispersion relations of the crystal-field excitations in cubic
antiferromagnets CeTe, CeSe, and CeS have been investigated by inelastic
neutron scattering using single crystalline samples. The Fourier transform of
the magnetic exchange interaction $J(q)$ obtained from the crystal-field
dispersion is largely different from that of the mean-field interaction
obtained from the N\'eel temperature and the Weiss temperature. From detailed
reexamination of the magnetic susceptibility and these $J(q)$ relations, we
conclude that the magnetic exchange interaction is dependent on the
crystal-field levels. The interaction associated with the $\Gamma_8$ excited
state is stronger than that with the $\Gamma_7$ ground state.
