Putative listeria isolates on selective agars from standard or screen positive enrichments are purified on non-selective agar and confirmed by conventional identification tests or by a battery of such tests in kit form. Isolates may be rapidly confirmed as L. monocytogenes (or not) by using specific test kits. Subtyping of L. monocytogenes isolates is optional except for FDA isolates, which have to be typed serologically, and by pulsed-field gel electrophoresis (PFGE) and by ribotyping. Non-obligatory pathogenicity testing of L. monocytogenes isolates is described.