Primary malignant lymphoma of the urinary bladder is very rare. Less than 100 cases have been reported; most are B-cell lymphomas. We report a case of primary T-cell lymphoma of the urinary bladder in a patient with a history of schistosomiasis. The patient is a 52-year-old man with suprapubic pain and hematuria. Examination revealed a large suprapubic mass. Computed tomography scan of the pelvis showed a large lobular mass occupying the urinary bladder. No pelvic or abdominal lymphadenopathy was noted, and results of metastatic workup were negative. The patient underwent a transurethral biopsy of the bladder mass that revealed a diffuse large cell lymphoma that was negative for the B-cell marker L-26 (CD 20) and positive for the T-cell marker CD-3. Polymerase chain reaction studies of the paraffin-embedded tissue revealed rearrangement of the T-cell receptor gamma gene. The patient was administered cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOPP) chemotherapy and currently is being treated. This case represents, to our knowledge, a very rare primary lymphoproliferative neoplasm of the urinary bladder that might represent an unusual immune response to schistosomiasis.