Three Iranian natural zeolites were characterized and evaluated for their abilities to take up Ba+2, Ca+2, K+ and Na+ from radioactive waste waters. The distribution coefficient values (Kd) of the cations were measured and investigated as a function of pH. Four different cationic forms (Na, K, NH4, and Ca) were also prepared and theirKd values were determined. Some cations such as potassium presented highKd values both in natural and exchanged zeolites. In sodium and ammonium exchanged forms theKd values increased between 7 to 100 times with respect to the untreated zeolite.