Caltumar bentonite (Northwestern Turkey) contains mainly dioctahedral smectite (montmorillonite) and opal-C and minor amounts of feldspar, biotite and amphibole. It is a type of Ca-bentonite. The rheological properties of Caltumar bentonite were studied in the presence of bisallylmalonamide / acrylacid (BAC) polymers. Bentonite clay sludge coated with BAC polymer is recommended in industry as it produces high viscosities. Besides, the measurement of the rheological properties of Calturnar bentonite (CAL), BAC and CAL + BAC have been examined in detail with X-ray diffraction (XRD), infrared spectra (IFT-IR), differential thermal and thermogravimetric analyses (DTA and TGA). All the results have been discussed by taking the interaction between the clay and the polymer molecules into consideration.