The　flow　injection　analysis　of　NADH　was　developed　based　on　its　inhibitory　effect　on　a　luminol-potassium　hexacyanoferrate(III)　chemiluminescence　(CL)　system.　Under　the　optimum　conditions,　the　decreased　CL　intensity　was　linear　to　the　NADH　concentration　in　the　range　of　5.0　x　10(-8)-2.0　x　10(-5)　mol　l(-1).　The　relative　standard　deviation　was　1.24%　for　eight　determinations　of　1.0　x　10(-6)　mol　l-(1)　NADH　and　the　detection　limit　(3s(b1)/S)　was　2.0　x　10(-8)　cool　l(-1).　The　study　of　interfering　substances　was　also　performed　and　the　method　was　applied　to　the　direct　determination　of　trace　amounts　of　NADH　in　synthetic　samples　with　satisfactory　results.　Moreover,　the　inhibitory　mechanism　of　CL　was　investigated　with　CL　spectra,　fluorescence　spectra　and　UV-visible　absorption　spectra.　(C)　2002　Published　by　Elsevier　Science　B.V.