In adult T-cell lymphoma/leukemia (ATLL), the neoplastic lymphoid cells are usually medium-sized to large, often with pronounced nuclear pleomorphism compatible with the diagnosis of diffuse pleomorphic peripheral T-cell lymphoma. We describe here 11 patients with the rare morphologic variant of ATLL, angioimmunoblastic T-cell lymphoma (AILT)-like type. The examined lymph nodes showed proliferation of high endothelial venules and presence of various infiltrating inflammatory cells including plasma cells and eosinophils. The lymphoma cells were medium-to-large size with clear cytoplasm. These findings were suggestive of AILT. However, immunohistochemical features of AILT, namely, CD10 and CXCL13 expression in lymphoma cells and proliferation of CD21-positive follicular dendritic cells, were not detected. Two cases were CXCR3-positive, whereas 9 expressed CCR4, which are usually positive in ATLL. All patients were positive for antiadult T-cell leukemia/lymphoma-associated antigen, which is a specific antibody for human T-cell lymphotropic virus type-I. Southern blot analysis revealed proviral DNA integration in lymphoma cells in 9 patients. The latter was not evident in the first biopsy of 2 patients but in the second biopsy obtained within several months after the first biopsy revealed definite proviral integration. Almost all patients showed aggressive clinical course and poor survival (median survival: 5 mo). This is the first report of ATLL with AILT-like morphologic features.