The adsorption of F- ions on the (311) face of Ag single-crystal electrodes was studied by capacitance measurements in NaF + KPF6 mixed electrolyte solutions of general composition c(NaF) + (0.04 - c)KPF6 mol dm-3. Capacitance values for the base solution were integrated twice from the potential of zero charge while those of solutions containing NaF were back-integrated from the range of negative charges. Surface excesses of adsorbed F- were obtained by differentiating surface pressure curves, and fitted by means of a virial isotherm. The results showed that F- ions are adsorbed on the (311) face similarly to the (110) face but with noticeable differences. The second virial coefficient B is lower and the rate of change of DELTA(ad)G-degree with charge is smaller. This can be explained in terms of higher partial charge transfer from F- to the (311) face of Ag on account of its higher electronegativity (work function). Comparison of the slopes of E(min)-c (NaF) plots for different faces suggests the following order of F- adsorption : (110) < (311) < (100) < (111), tentatively interpreted as related to the opposite order of crystal face "hydrophilicity".