A bismuth film electrode (BiFE) prepared ex-situ on a supporting glassy carbon electrode exhibited convenient electroanalytical performance for voltammetric measurement of selected aminosalycilate drugs. The reduction behaviour of aminosalycilate drugs was studied in aqueous solutions within the pH range of 4-6. The voltammetric responses were compared with those obtained at the bare glassy carbon electrode under identical conditions. In the square-wave voltammetric operation mode the BiFE showed a linear response in the concentration range of 5 x 10(-6) to 3.5 x 10(-4) and 1 x 10(-6) to 5 x 10(-4) M for sulfasalazine and olsalazine, respectively. Its electrode surface revealed auspiciously high stability and remarkable reproducibility in the rapid analysis of aminosalycilate drugs. Finally, the BiFE was satisfactorily applied for direct quantitation of azo prodrugs in real pharmaceutical samples. (C) 2009 Elsevier Ltd. All rights reserved.