We have studied the adsorption of p-aminophenol on poly(aryl ether ketone) containing pendant carboxyl groups (PEK-L). The pH effect, adsorption kinetics, isotherms, and thermodynamics are investigated in batch experiments. The kinetics of the adsorption follows a pseudosecond-order model. Langmuir and Freundlich isotherms are employed to describe the adsorption process, indicating that the former fits the data better. The thermodynamic functions, Delta G degrees, Delta H degrees, and Delta S degrees are calculated. The method is applied to the determination of p-aminophenol in drug tablet samples, and the accuracy is asses sed through recovery experiments.