Black oesophagus is a rare pathological condition of unknown aetiology characterised by a full length, circumferential black discolouration of the entire oesophageal mucosa. The disease is sporadically encountered during upper gastrointestinal endoscopy. We used conventional histology, enzyme histochemistry and immunohistology to examine five autopsy cases (four males, one female; age range 43-86 years) of black oesophagus. On microscopical examination, the esophageal mucosa was entirely necrotic with demarcation by a leukocytic infiltrate in the upper submucosa. This infiltrate was dominated by neutrophilic granulocytes and scattered macrophages lacking haemosiderin deposits, placing the noxious mucosal injury in a time frame of approximately 24-72 h prior to death. Black oesophagus was established as the immediate cause of death in one case due to desanguination from the oesophagus and significantly contributed to the fatal outcome in a second case. Apart from a history of chronic alcohol consumption in four cases, no other pre-existing pathological or debilitating conditions could be established. The remarkably consistent pathomorphological picture of the disease seems to be the result of impaired microcirculation of the oesophageal mucosa due to prolonged hypotension of variable aetiology. The diagnosis of black oesophagus requires exclusion of other causes such as ingestion of caustic materials and should be based on histological examination.