In this study, the effect of carboxymethyl cellulose (CMC) used as stabilizer in the preparation of coal-water slurries on the stability has been investigated. Experiments have been carried out on the coal samples which differ in rank. Besides two different Turkish Lignites (Soma and istanbul) also a bituminous coal (Thermal Code No. 434) of Turkish origin (Zonguldak) with medium volatile matter has been used. The results of the experiments showed that polymeric anionic CMC agent has much greater effect on the stability of CWS prepared from bituminous coal. Also, we found that inorganic mineral matters were able to be used as a stabilizer for preventing the sedimentation and separation of CWS. (C) 2004 Elsevier Ltd. All rights reserved.