The adsorption of three reactive dyes, Remazol Red, Rernazol Blue and Rifacion Yellow, from aqueous solutions using fly ash as an adsorbent was studied in an agitated batch system to investigate the influence of two parameters viz., adsorbent dosage and particle size on the removal efficiency of the reactive dyes. Firstly, the adsorbent was characterized with using several methods such as SEM, XRD and FTIR. The FTIR suggested that the dye on fly ash is probably indicating fly ash/dye cornplexation. XRD pattern of fly ash consisted of mainly quartz, mullite with some magnetite and calcite. Surface morphology of fly ash and dye loaded fly ash were obtained with SEM. Secondly, the percentage of dye removal at equilibrium, p, was determined with respect to these two parameters with a constant initial dye concentration of 100 mg/L, agitation speed of 250 rpm, pH 6 and temperature of 22 degrees C for a period of 48 h. The experimental data were treated with two simple empirical models used for predicting the percentage of the dyes adsorbed on the fly ash. Both models showed good correlation coefficients but the best model which determined the p values can be selected on the basis of the standard deviation of the calculated and experimental values.