To rapidly, simply and specifically detect and identify Listeria monocytogenes from food samples, an immunochromatographic assay, based on gold-labeled monoclonal antibodies directed against an antigen common to all serovars of L. monocytogenes, was used. All strains of L. monocytogenes serovars showed a positive reaction to the assay, but all other gram positive and negative bacteria did not. The detection limit of the assay was in the order of 10(6) cfu/ml in fluid medium. The assay could simply and rapidly identify L. monocytogenes within 30 min by a pure culture without special instruments. Even if the selective enrichment cultivation was employed for the isolation and growth of bacteria from food materials, the application of the assay system could detect and identify L. monocytogenes precisely in various food materials within 2 to 3 days.