Brain samples of 849 wild ruminants (654 roe deer, 189 red deer and 6 chamois) from Bavaria were examined for the occurrence of encephalopathies caused by bacteria, using cultural, serological and genetic methods. In addition, 87 brain samples were investigated histologically for clarification of the pathogenetic relevance of specific microorganisms. Using conventional bacteriological methods, 464 different bacteria were isolated. 229 of them could be differentiated to the genus level and 235 to the species level. Totally, 35 different bacteria species were isolated, most frequently Micrococcus spp., Bacillus spp. and E. coli. Listeria spp. were detected in 43 brain samples (37 from roe deer, 5 from red deer and 1 from chamois). Sixteen strains were identified as L. innocua, 14 as L. monocytogenes, 9 as L. seeligeri and 4 as L. grayi. Serological investigations of L. monocytogenes showed that 9 strains belong to serotype 1/2a and five to 4b. Analysis of the geographical distribution of the Listeria findings indicate a statistically significant (p<0.011) regional aggregation in Unterfranken (prevalence for roe deer: 12.2%, versus 4.5% in Oberbayern-Schwaben, 6.1% in Niederbayern-Oberpfalz and 0% in Oberfranken-Mittelfranken). The histological investigation (HE staining) of 87 tissue samples contaminated with encephalitis relevant bacteria showed inflammation of different severity (mild meningitis and choroiditis (n = 26) to moderate (meningo)encephalitis (n = 13)) in 41 cases.