In this work, sorption of uranium ions on volcanic tuff collected from the deposits located at the Tendurek of Eastern Turkey was investigated in batch technique. The effect of different parameters such as pH of the medium, contact time, uranium concentration and temperature were investigated. The maximum removal of U(VI) was found to be 68% at pH 5.0, initial U(VI) concentration of 75 mg L(-1) and 30 degrees C. Thermodynamic parameters, such as enthalpy of adsorption Delta H degrees, free energy change Delta G degrees and entropy change Delta S degrees have been also calculated and interpreted. The suitability of the Langmuir, Freundlich and Dubinin-Radushkhevic adsorption models to the equilibrium data was investigated for uranium-volcanic tuff system. The results suggest that volcanic tuff can be used as efficient and cost effective adsorbents for uranium ion removal.