A calcium bentonite from Kutahya region (Turkey) was activated with Na2CO3 at various ratios (1, 2, 2.5, 5, 10, 15g/100 g bentonite). Due to ion exchange, the original Ca-bentonite was converted to Na-bentonite by Na2CO3 when the Na2CO3/bentonite ratio was 2.5% (2.5 g Na2CO3/100 22g bentonite, A2.5). Na-bentonite (A2.5) obtained by soda activation was treated with 3 g CaCl2/100 g bentonite and converted to Ca-bentonite again. The products were investigated by chemical analysis, X-ray diffraction and micropore analysis. It was observed that the cation exchange capacity (CEC) did not change until the soda ratio was 2.5 %. After this value the CEC decreased rapidly. The main montmorillonite hkl diffraction reflections were changed by Na2CO3 and CaCl2 treatments. This showed that ion exchange was realized. It was observed that the specific surface area decreased from 49.34 m(2)g(-1) to 29.92 m(2)g(-1) by Na2CO3 and increased from 29.92 m(2)g(-1) to 70.31 m(2)g(-1) by CaCl2. In addition, it was determined that Na2CO3 activated Kutahya Ca-bentonite can be used as drilling mud.