In connexion with the separation of Listeria innocua (Seeliger and Schoofs, 1977) from Listeria monocytogenes (Murray et at., Pirie, 1940), resulting epidemiological and epizootological problems are discussed. L. innocua is apathogenic when conventional experimental models for testing Listeria monocytogenes are used. Under special conditions, i.e. use of suckling mice, strain Welshimer of L. innocua produced localized encephalitis (Pato?ka et al., 1979). The peculiarities of L. innocua justify further studies at the immunological, infectious-pathological and genetical level. A description of the new species is given in the appendix of this paper.