The diffusivity and activity coefficient of oxygen in liquid antimony, bismuth and antimony-bismuth alloys were determined from coulometric titration experiments, which were performed in the temperature range from 985 to 1185 K. The diffusivity in pure metals (in cm2/s) is: Dbi,O =(9.04 ? 1.82)?10-3 exp (-49115?1809/RT) DSb,O(2.87?0.22)?10-4 exp (-16720?677/RT). The standard free energy of solution of oxygen in liquid antimony, bismuth and antimony-bismuth alloys according to the reaction ? O2 (g) = O (infinite dilution) is calculated. The activity coefficient of oxygen was calculated at 1085 K as a function of the alloy composition. It was demonstrated that Wagner's model with one adjustable parameter h gave a satisfactory description of the experimental data. nema