Adsorption of poly(amido amine) (PAMAM) dendrimers at water–silica interfaces and the resulting self-organization on this type of substrate is discussed. Investigations with optical reflectivity and atomic force microscopy (AFM) reveal that dendrimers form monolayers of low coverage on such surfaces with liquid-like structure. The nearest neighbor separation distance in these layers is dictated by screened Coulomb repulsion forces between the adsorbing dendrimers. This effect rationalizes the strong increase of the adsorbed amount with the ionic strength and pH. These layers are stable for high dendrimer generations, while they can become unstable for lower generations.