Measurements of the thermal conductivity of superconducting specimens of bismuth-thallium (BiTl: 3.92 at% Tl in Bi) and bismuth-lead (BiPb: 4.00 at% Pb in Bi) were made from 1.5 to 300 K, both in the normal and the superconducting states, and the effect of plastic deformation on the thermal conductivity of these specimens was studied. The data for BiTl and BiPb show that the heat carriers over a considerable range of temperature are essentially phonons but that electronic contributions are significant at low temperatures, both in the normal and superconducting states. At higher temperatures, appreciably above Kmax, the electronic contributions can be significant because of thermal excitations across a band gap. The Debye temperature, θD, is altered for BiTl and BiPb, compared to that of pure Bi. Plastic deformation greatly affected the thermal conductivities of the two systems. In addition, the band gap and θD were increased with plastic deformation. © 1986.