Synovial sarcomas are rare soft tissue malignancies that most commonly affect the extremities in the vicinity of large joints. These malignancies typically occur in adolescents and young adults between the ages of 15 and 40 years.(1,2) Historically they are believed to originate from primitive pluripotent mesenchyme capable of synovial differentiation. This belief is consistent with the malignancy's origin from sites devoid of normal synovium, such as the pleural cavity. A variety of pleural cavity sarcomas have been described, including liposarcoma,(3) chondrosarcoma,(4) osteosarcoma,(5) and malignant schwannoma.(6) Pleural synovial sarcoma, however, is a much rarer entity. In fact, pleural synovial sarcoma was first described only 6 years ago(7) and has not yet been reported in the surgical literature. Because of its rarity, pleural synovial sarcoma is often mistaken for the histologically similar malignant mesothelioma, the most common of the pleural neoplasms. This is a critical distinction, because synovial sarcoma may be extremely aggressive. Studies in the last 10 years have shown it to be extremely sensitive to ifosfamide-based chemotherapy, and survival of patients with synovial sarcoma has recently increased with chemotherapy, with 5-year survivals now as high as 57%.(8-10) In this report, we describe 3 cases of synovial sarcoma of the pleura. Clinical findings are correlated with pathologic features, including immunohistochemical stains and fluorescence in situ hybridization (FISH) for the identification of the diagnostic chromosomal translocation, t(X;18)(p11.2;q11.2). This delineation of the clinical and pathologic aspects of this rare, newly recognized tumor should increase awareness among the surgical community.