Primary peritoneal sarcoidosis. A 14-year-old male was admitted for the evaluation of tense exudative ascites. Despite thorough evaluation, the diagnosis remained cryptic until peritoneoscopy revealed diffuse studding of the entire visualized peritoneum with multiple miliary nodules, and peritoneal biopsy demonstrated multiple noncaseating epithelioid granulomas. After other causes were excluded, a diagnosis of sarcoidosis was considered and confirmed with classic endobronchial findings at bronchoscopy. Involvement of the peritoneum with sarcoidosis is rare and, to our knowledge, only one other case describes this as the initial manifestation of this disease. 