Various strategies based on the use of chemically modified electrodes for the development of amperometric biosensors are described. Particular emphasis is placed on materials capable of catalyzing the oxidation of NADH and coupling these with enzymatic activities for biosensor construction. In terms of electrocatalysts, the discussion will centre on electrodeposited films of 3,4-dihydroxy benzaldehyde (3,4-DHB) and related analogs as well as on electrodeposited films of transition metal complexes of 1,10-phenanthroline-5,6-dione (phen-dione). Electrodeposited films of these materials have been coupled to the enzymatic activity of aldehyde dehydrogenase and alcohol dehydrogenase for the development of biosensors for aldehydes and ethanol, respectively.