Adsorption of Astrazone Blue FRR (Basic Blue 69) and Teflon Blue ANL (Acid Blue 125) was investigated using a hybrid adsorbent that was prepared by pyrolysing a mixture of carbon and fly ash in 1:1 ratio. A 2 4 full factorial central composite design was successfully employed for experimental design and analysis of the results. The combined effect of pH, temperature, particle size and time on the dye adsorption was studied and optimized using response surface methodology. The optimum pH, temperature, particle size and time were found to be 12.8, 27.75 degreesC, 0.0555 mm, 230 min, respectively for basic blue and those for acid blue 25 were 1.5, 27.5 degreesC, 0.0565 mm and 245 min, respectively. Complete removal (100%) was observed for both the dyes using the hybrid adsorbent. (C) 2004 Elsevier B.V. All rights reserved.