The adsorptive and electrochemical behaviors of medecamycin were investigated on a glassy carbon electrode (GCE) pretreated by anodic oxidation at +1.8 V for 5 min in 0.025 mol l(-1) NH(3)-NH(4)Cl (pH 8.6) solution. An adsorptive stripping voltammetric method for the determination of medecamycin at the pretreated glassy carbon electrode has been developed. Medecamycin was accumulated in NH(3)-NH(4)Cl buffer (pH 9.0) at a potential of -0.7 V (vs. saturated calomel electrode (SCE)) for a certain time, and then determined by second-order differential anodic stripping voltammetry. The second-order differential anodic stripping peak current at +0.72 V was proportional to the concentration of medecamycin in the range 2.0 microg ml(-1) to 50.0 microg ml(-1). The detection limit (three times the signal-to-noise) was 1.0 microg ml(-1) and the relative standard deviation of the results was 3.28% for eight successive determinations of 10.0 microg ml(-1) medecamycin. This method has been applied to the direct determination of medecamycin in commercial tablets and spiked urine samples with satisfactory results.