In this paper we study the carrier contribution to the elastic constants in quantum wires of IV-VI semiconductors under parallel magnetic field on the basis of a newly derived electron dispersion law. It is found, taking quantum wires of PbS, PbSe and PbTe as examples, that the carrier contribution to the second and the third order elastic constants increases with increasing electron concentration and decreasing film thickness in various oscillatory manners. The magnetic field and the quantum wire structure enhance the numerical values of the said contribution. We have suggested an experimental method of determining the said contribution in quantum wire structures having arbitrary carrier dispersion laws. In addition the corresponding well known results for bulk specimens of relatively wide gap materials in the absence of a magnetic field have been obtained as special cases of our generalized analysis under certain limiting conditions. © 1997 Elsevier Science Ltd. All rights reserved.