ABSTRACT. The Listeria monocytogenes-carrying rates were 100% for listeriosis patients and 1.3% for healthy humans. The L. monocytogenes contamination rates for retail sliced beef (34.2%) and pork (36.4%) were significantly higher (p<0.05) than those for cattle (2.0%) and pigs (0.8%) and for cattle (4.9%) and swine (7.4%) carcasses. The percentages of serotypes 1/2a, 1/2b and 4b which are most dominant in human patients were high in isolates from fresh (90.0%) and processed (100%) fish and shellfish and imported natural cheese (96.7%). -KEY WORDS: Listeria monocytogenes, meat, serotype J. Vet. Med. Sci. 60(12): 1341-1343, 1998 A 1-g portion of stool and intestinal content samples was enriched in 9 ml UVM medium (Difco Laboratories, Detroit, Mich.) or EB medium (Difco). The swabs were each added to 9 ml of an enrichment medium. Samples of natural cheese (25 g) and meat and fresh and processed seafoods (10 g each) were each placed in a stomacher bag containing 225 ml or 90 ml of the enrichment medium, and homogenized for 1 min with a stomacher. The stomacher bags were incubated at 30°C for 48 hr. Two to three loopfuls of the cultured enrichment medium from the stomacher bags were streaked on a plate of Oxford agar medium (Oxoid, Unipath Ltd., Basingstoke, Hampshire, England) or PALCAM agar medium (Merck Co., Inc., Rahway, N.J.) supplemented with amphotericin B (Sigma Chemical Co., St. Louis, Mo.) at a concentration of 6 µg/ml to inhibit the growth of mycetes and the plates were incubated at 30°C for 48 hr. Slightly flat colonies with brownish color in the periphery, which is characteristic of Listeria, were subcultured on Tryptose Agar medium (Difco). The colonies developed on Tryptose Agar medium were observed under a low power microscope with obliquely reflected light and blue greenish colonies were selected [12]. Identification was carried out by Gram staining, catalase and VP tests, observation of umbrella-like growth and motility in semiliquid Brain Heart Infusion Agar medium (Difco), utilization of rhamnose, xylose and mannitol, β-hemolysis on 5% sheep blood Tryptic Soy Agar medium (Difco) and the CAMP test [12] with Staphylococcus aureus JTE 88-221 and Rhodococcus equi JTE 89-387 .The factor sera were prepared by hyperimmunizing rabbits (Japan Laboratory Animals, Inc., Tokyo) with each of 12 reference strains, L. monocytogenes JTE 88-178 to JTE , by the method of Seeliger and Höhne [11]: 11 kinds of somatic (O) antigen factor sera and four kinds of flagellum (H) antigen factor sera were obtained. Serotyping was conducted by O and H agglutination reactions on microplates [1]. Description of the serotypes of the isolates was followed after Seeliger and Höhne [11].As shown in Table 1, the L. monocytogenes-carrying rates