A biosensing system based on (alpha-glucosidase (AG) activity was developed by using bismuth film modified glassy carbon electrode (BiFE). AG enzyme was immobilized on the BiFE by means of gelatin membrane and the activity was measured by the following of liberated 4-nitrophenol from the 4-nitrophenyl-alpha-D-glucopyranoside (PNPGP) which is the synthetic substrate of the enzyme at the working potential of -950 mV. The proposed system was used as an AG based biosensing system. Experimental data showed that the response current of 4-nitrophenol obtained at the BiFE was linear in concentration range between 0.033 and 0.33 mM of PNPGP. Before examining the analytical characteristics, pH optimization of the AG-biosensor was also performed. Furthermore, the proposed method was applied to analyze two different AG inhibitors (Amaryl and Acorbose) which are important in Noninsulin-dependent diabetes mellitus (NIMM). (C) 2007 Elsevier B.V. All rights reserved.