Electrical resistivities of liquid sodium-potassium and sodium-rubidium alloys have been determined by the Thomson bridge method. The liquid metal was enclosed in a stainless steel tube. The two resulting resistivity vs. concentration curves can be roughly represented by Nordheim parabolas, of which that for the sodium-rubidium alloys is the higher. The curves are slightly asymmetric, the maximum being displaced towards larger concentrations of the heavier element. The results are qualitatively interpreted on the basis of the Ziman formalism, using structure factors according to Ashcroft and Lekner and pseudopotentials according to Animalu and Heine.