Ninhydrin　was　found　to　exhibit　chemiluminescence　(CL)　when　it　was　oxidized　with　hydrogen　peroxide　in　neutral　or　weakly　acidic　solution.　Copper(II)　and　Co(II)　can　catalyse　the　CL　reaction,　on　the　basis　of　which　ppb　levels　of　Cu(II)　and　Co(II)　can　be　determined.　In　the　presence　of　Cu(II),　some　amino　acids　enhanced　the　CL　reaction,　whereas　others　inhibited　the　CL　reaction　in　the　presence　of　Co(II).　A　flow-injection　system　with　CL　detection　was　developed　for　the　determination　of　some　amino　acids.　The　mechanism　of　the　CL　reaction　is　discussed.