The present research involves the determination of the activities of aluminium in aluminium. + gallium + bismuth + antimony alloys over the temperature range (1173 to 1323) K using a concentration cell technique involving the chloride electrolytes. The measured activities in the system exhibit positive deviation from ideal behaviour over the entire range of studied composition. The deviation decreases progressively with increase in the Sb contents of the alloys for similar Al compositions. The latter has also been found to decrease substantially with the decrease of Al contents and increase in temperature of the system. The present research also investigates the application of the excess stability function to the experimental compositions in order to ensure the stability of the liquid phase alloys. (C) 2004 Elsevier Ltd. All rights reserved.