m s A immunocompetent man was referred to our department under the suspicion of disseminated peritonitis carcinomatosa. His physical examination was unremarkable except for slight abdominal distention. Contrastenhanced computed tomography (CT) revealed a small amount of ascites and diffusely thickened peritoneum with omental thickening (Figure A). F-18 fluorodeoxyglucose (FDG)-positron emission tomography (PET) also showed diffuse FDG uptake throughout the intraperitoneal cavity, including greater omentum and mesenterium, and slight uptake in the right supraclavicular lymph node, which strongly suggested the possibility of peritonitis carcinomatosa with metastasis to the supraclavicular lymph node (Figure B). Esophagogastroduodenoscopy and total colonoscopy showed no signs of malignancy at all. The amount of his ascites was too small for abdominal paracentesis. Exploratory laparoscopy was essential to obtain ascites intraoperatively and peritoneal biopsy specimens. Laparoscopy showed the diffusely thickened peritoneum with small white nodules, and intestines were strongly adhesive to the omentum and mesenterium (Figure C). A slight amount of yellowish serous ascites was also found in the Douglas’ pouch. The macroscopic appearance indicated tuberculosis rather than malignancy; however ascites cytology was negative. Peritoneal histology showed epitheloid granuloma formation but no findings of caseating granuloma. No signs of Mycobacterium infection were observed from the ascites culture or immunostaining specimens of the peritoneum. Therefore, the right supraclavicular lymph node was biopsied, which was enhanced in the FDG-PET/CT images. Granulomatous inflammation with necrosis was confirmed histopathologically. Mycobacterium tuberculosis infection was proved both from immunochromatography and liquid culture. We concluded that tuberculous peritonitis (TBP) caused the thickness and adhesion of the peritoneum. Quadruple drug therapy had been administered for 26 weeks. The CT scan showed remarkable improvement in the peritoneum immediately after the antituberculosis therapy. No recurrence had been observed at all since then. TBP is a well known site for extrapulmonary infection caused by Mycobacterium tuberculosis. TBP is the sixth most common extrapulmonary site in the United States.1 The risk is increased in patients with cirrhosis, HIV infection, and continuous peritoneal dialysis.2,3 However, there were no risk factors as described above in this case. Diagnosis of TBP remains a challenge because of its insidious nature. The gold standard for the diagnosis is laparoscopy and culture growth of Mycobacterium on peritoneal biopsy. The combination of acroscopic appearance and histologic findings has the senitivity of more than 90%,4 however we could not reach the final diagnosis after the laparoscopy and biopsy. Diagnostic therapy would be taken into consideration in this case, even if the cervical lymph node specimens showed no proof of tuberculosis infection.