this study, adsorption of AV90 (C. I. Acid Violet 90) and AY194 (C. I. Acid Yellow 194) acid dyes using eggshell was investigated. The effects of various parameters such as pH (2-7), adsorbent dosage (3-25 g/L), particle size (30-710 mu m), temperature (20-40 degrees C), initial dye concentration (50-200 mg/L) were examined. The highest dye removal was obtained at pH 2 for both of the dyes. The Langmuir, Freundlich and Temkin adsorption isotherm models were applied to the experimental equilibrium data and the isotherm constants were determined. The highest dye removal was observed at 20 degrees C and the adsorption capacities and percentage removal of eggshell for AV90 and AY194 were obtained as 9.97mg/g, 9.60 mg/g and 82.3 % and 91.5 % at 20 degrees C, respectively. The adsorption kinetic of dyes was acquired Pseudo second order model.