Serious infection with the bacterium L. monocytogenes mainly manifests as sepsis and/or meningitis. A particular entity is Listeria brain stem encephalitis, which is characterized by progressive brain stem deficits. The condition is fatal unless early treated. The purpose of the present study was to assess the incidence of brain stem encephalitis in a population-based listeriosis material. Medical records from 212 of the 240 patients with serious listeriosis reported in Norway from 1977 to 2000, as well as autopsy material from 8 of these patients, were available. This material was searched for clinical and neuropathological evidence of brain stem infection. Findings indicating brain stem encephalitis were present in 19 of the 172 patients with adult listeriosis (11%) but none of the 40 pregnancy-related listeriosis cases. None of the 19 patients had been diagnosed with Listeria brain stem infection originally. We conclude that brain stem encephalitis is relatively common in this Norwegian listeriosis material.