Lactate dehydrogenase (EC 188.8.131.52) has been immobilized in polyacrylamide gels over a platinum grid matrix. The immobilized enzyme is used to oxidize L‐lactate in the presence of nicotinamide adenine dinucleotide (NAD+) and femcyanide. The NADH produced is then chemically oxidized back to NAD+by ferricyanide. The coupled reduction of ferricyanide ions to ferrocyanide ions results in a measurable electrochemical potential. This measurable zero‐current potential is found to be Nernstian in nature and directly proportional to the logarithm values of L‐Iactate concentration over the range of 2 × 10−5to 5 × 10−2M. The results indicate that immobilized lactate dehydrogenase can be incorporated into a system to detect L‐Lactate acid in aqueous solutions.