Background: Peripheral T-cell lymphoma, not otherwise specified (PTCL, NOS) is a rare neoplasm that typically presents as generalized lymphadenopathy. PTCL, NOS presenting as malignant ascites is rare. Methods: A 61-year-old African-American man with past medical history of HCV, cryoglobulinemia, and cryptococcal pneumonia was admitted for dyspnea on exertion over a period of 1 month and new onset of abdominal distension. Results: Ascites, splenomegaly, hepatomegaly and extensive lymphadenopathy were found by imaging. Paracentesis obtained 1.3 liter of abdominal fluid, the cytologic evaluation showed a monomorphic population of intermediate-sized lymphoid cells with irregular to convoluted nuclear contours. Fluid sent for flow cytometry showed an abnormal T-lymphocyte population expressing CD4, weak surface CD3 and absence of CD7. PCR studies of ascitic fluid detected a clonal T-lymphocyte population with T-cell receptor gamma gene rearrangement. Serologic testing for human T lymphotropic virus (HTLV) was positive for HTLV-II. Subsequent bone marrow biopsy revealed lymphomatous involvement. CD30 and ALK-1 immunostaining were negative. This case was classified as PTCL, NOS. Conclusions: PTCL, NOS can have unusual clinical presentation such as ascites and pleural effusion, and may also occur as a complication of immunodeficiency state. Further studies are needed to determine if HCV or HTLV-II viral infection is associated with PTCL.