Adsorption isotherms of five different sensitizing dyes have been obtained at monodisperse AgBr grains in a wide pAg region separately at (100) and (111) crystal faces. From the experimental data, values of the maximum surface coverage and of the heat of adsorption were calculated. Some of the adsorption isotherms deviated considerably from the ideal Langmuir type either by an unusually steep initial slope or by an inflexion preceding the Langmuir branch. Geometric-statistical considerations led to on interpretation of the observed deviations which are caused either by a competition of two different geometric orientations (e.g. flat/edge-on) or by a competition of two separately adsorbed components of the system (e.g. dye/Ag ions).