A biosensor for monitoring alkaline phosphatase (ALP) enzyme activity was developed by using bismuth film electrode (BiFE) as transducer. The aim was to test the possible applications of BiFE as transducer in this biosensing platform. ALP was immobilized onto the BiFE electrode by means of gelatin which was then crosslinked by glutaraldehyde. The measurement was based on monitoring of p-nitrophenol which was released after enzymatic reaction of p-nitrophenyl phosphate (pNPP) substrate. The effect of enzyme activity (in Unit) was examined for 100 mu M of pNPP substrate and a good linearity was observed between 1.28 and 4.26 U activities with the equation of y = 0.214x - 0.201 and R(2) = 0.998 where x and y show enzyme activity in unit and current response in mu A respectively. Analytical characteristics were also examined after the optimization of experimental parameters.