The Gibbs adsorption equation has been used in conjunction with surface tension measurements on silver wires to determine the adsorption isobar of oxygen on silver at a pressure of 16 cmHg over the temperature range 650-850 �C. The results show the existence of a surface concentration of oxygen of 2 x 1015 atoms oxygen per cm2. The value of ΔH for the equilibrium between adsorbed and dissolved oxygen has been estimated as 20.6 kcal. This value in conjunction with the heats of formation and solution of Ag2O in silver permit the h3at of adsorption to be determined as 10.5 kcal per g-atom of oxygen.