A 31-year-old renal transplant recipient developed an unusual T-cell lymphoproliferative disorder 3 years after transplantation. The neoplasm involved the spleen, without concomitant hepatomegaly, lymphadenopathy, or obvious bone marrow involvement. Peripheral blood involvement developed after splenectomy. Immunophenotypically, the neoplastic cells expressed CD2, CD3, CD7, CD16, CD45, CD56, and the gamma/delta T-cell receptor on the surface membrane. The neoplastic cells were negative for surface membrane CD4, CD5, and CD8. Serologic and/or DNA analyses for viruses, including Epstein-Barr virus, human T-cell lymphotropic virus-1, human immunodeficiency virus, and human herpesvirus-6, were negative. Cytogenetic findings included a translocation breakpoint at chromosome 7p15, consistent with involvement of the T-cell receptor gamma-chain locus. Although gamma/delta T-cell lymphomas have been reported to have a predilection for hepatosplenic localization, this is the first well-documented case to be described in the setting of posttransplantation immunosuppression.