The electrooxidative behavior of amoxicillin was investigated on a poly(acridine orange) modified glassy carbon electrode from pH 5.0 to 8.0 by cyclic, differential pulse, and square wave voltammetry. The electrochemistry of amoxicillin was shown to be irreversible and diffusion controlled using the poly(acridine orange) modified electrode. Amoxicillin was determined by differential pulse and square wave voltammetry in 0.04M Britton-Robinson buffer at pH 5.0. Calibration curves were linear between 0.4 and 20 mu M with detection limits of 1.87x10(-3)mu M and 1.55x10(-2)mu M for differential pulse voltammetry and square wave voltammetry, respectively. The developed methods provided high selectivity, precision, and accuracy and were employed for the determination of amoxicillin in pharmaceuticals and human serum.