Disclosed are silane-modified urea derivatives which can be produced by reacting diisocyanates with aminosilanes, hydroxysilanes, or mercaptosilanes. The inventive silane-modified urea derivatives are suitable especially for use as auxiliary rheological agents, preferably as thixotropic agents for silane-crosslinking systems, particularly for single-component and two-component adhesives and sealants, paint, lacquers, and coating while causing substantially no increase in viscosity, not being subject to discoloring, being reactive, and positively influencing mechanics.