Adsorption of cephalexin.H2O on the surfaces of activated carbon and bentonite (which is provided locally in Iraq) was studied. The purpose of the study is searching for surfaces that are highly applicable of adsorption this compound which, taken in highly dozes, their results are some cases of poisoning. This study uses UV-Visible spectrophotometry to know the quantity of adsorption of these compounds on the employed surfaces at different conditions of temperature, pH, Ionic strength, quantity adsorbed, and particle Sizes. The shape of the isotherm obtained from the adsorption of cephalexin.H2O on bentonite and activated carbon was found to be comparable in all cases to the Freundlich and Langmuir equations was similar to S4-curve and L4- curve type according to Giles classification.The capacity of the adsorbents to adsorbing the cephalexin.H2O is in the following order:- Activated carbon < Bentonite The kinetic and thermodynamic parameters of adsorption will be calculated. The thermodynamic functions enthalpy ?H, Gibbs free energy ?G and entropy ?S were calculated and were explained in the mean of the structure formula of the adsorbents.