In this study the stability characteristics of uniformly elongating plastic jets exposed to axial electric currents are investigated. The objective of this study is to expand the results of previous analyses by Littlefield ["The effect of electromagnetic fields on the stability of a uniformly elongating plastic jet," Phys. Fluids A 2, 2240 (1990); "Finite conductivity effects on the MHD instabilities in uniformly elongating plastic jets," ibid. 3, 166 (1991); "Enhancement of stability in uniformly elongating plastic jets with electromagnetic fields," ibid. 3, 2927 (1991)] to include high levels of electric current, where thermal energy effects must be included. Coupling of the magnetohydrodynamic and thermal characteristics of the flow is accomplished through the variation of mechanical, thermal, and electrical properties with temperature. Phase change effects are also considered. The jet is assumed incompressible and perfectly plastic, with the Levy-von Mises criterion imposed to limit the effective stress. Solutions to the appropriate base flow are subjected to small axisymmetric disturbances, and linear perturbation theory is employed to determine the time evolution of these disturbances. Perturbations that grow the fastest in magnitude as time progresses are identified as the most unstable. Results of the analysis indicate that thermal effects can dramatically alter both the base and perturbed flow fields, as well as the growth rate of perturbations. © 1994 American Institute of Physics.