We report a case of purulent diffuse peritonitis in a patient who was affected by Hodgkin lymphoma, with no evidence of other abdominal diseases. This is a 54 y. old. white male who was admitted to our department with a history of asthenia, recurrent fever, dysphagia and abdominal pain. In the plain abdominal radiology pneumoperitoneum was evident. Duodenal perforation suspicion was confirmed by anamne sis and plain radiology which showed the presence of intra abdominal air. Emergency exploratory laparotomy showed a purulent diffuse peritonitis, which relapsed after multiple surgical toilettes and peritoneal lavage. A postoperative abdominal CT scan and histology of a biopsy taken during the second surgical operation showed a retroperitoneal Hodgkin lymphoma, which went to remission after chemotherapy. Considering the two simultaneous clinical manifestations (retroperitoneal Hodgkin lymphoma and peritonitis), we made two pathogenetic hypotheses: a) The retroperitoneal disease produced lymphatic stagnation and peritoneal transudation, which then was infected; b) The abnormal lymph nodes were infected and the abdominal cavity was contaminated from retroperitoneum from blood/lymphatic stream or by contiguity.