IRAS studies of CO adsorption on the Au(110)-(1 x 2) surface were performed as a function of CO pressure and sample temperature. It was found that with increasing coverage, the CO IRAS absorption shifts red from 2118 to 2108 cm(-1). Clausius-Clapeyron data analysis yielded a heat of CO adsorption (-DeltaH(ads)) of 10.9 kcal/mol at low coverages and 7.8 kcal/mol at coverages greater than 19%.