The radial profiles of the potential of mean force for the H3O+...Cl- pair are determined by constraint molecular dynamics of infinitely dilute high-temperature HCl aqueous solutions over a wide range of state conditions. The ion-pair association constant are consequently calculated and compared with those obtained from the most accurate recent electrical conductance experiments [Ho, P. C.; Palmer, D. A.; Gruszkiewicz, M. S. J. Phys. Chem. B 2001, 105, 1260-1266] at corresponding states. Resulting equilibrium constants between contact and solvent-shared ion-pair configurations indicate that more than 97% of configurations are contact ion-pairs. The adequacy of some simple fully electrostatic models to represent ion-pair association behavior in high-temperature aqueous solutions is also discussed.