The values of the orbit-dependent hyperfine-structure constants are given for the ground-state terms of the atoms B, C, O, and F. These values are obtained from multiconfiguration Hartree-Fock wave functions using a very limited number of excited terms. The excited terms are chosen from guidelines based on second-order perturbation theory. The results are in satisfactory agreement with available experimental data and accurate many-body perturbation-theory calculations for O. A physical explanation, in terms of the configuration-interaction model, is presented for the essential importance of non-core-polarization contributions to the Fermi contact term for these atoms. © 1973 The American Physical Society.