OBJECTIVE To characterize angioimmunoblastic T-cell lymphoma (AILT) on morphological, immunohistochemical and molecular grounds and its association with Epstein-Barr virus (EBV) in Pakistani patients. METHODS Case series. METHODS Histopathology section of the Department of Pathology and Microbiology, The Aga Khan University Hospital, Karachi from January 01, 1992 to December 31, 2002. METHODS Over a period of 11 years archival biopsy material of 13 AILT cases (lymph nodes), identified on the basis of histological and immunohistochemical criteria, using REAL and WHO classifications, were retrieved from the files of Department of Pathology. Immunophenotyping was carried out by using CD45 (LCA), two T-cell markers CD45RO (UCHL1; monoclonal) and CD3 (polyclonal). Polymerase chain reaction (PCR) was used to assess T-cell clonality for T-cell receptor (TCR)-b, g and immunoglobulin heavy chain (IgH) for FR2 and FR3 regions using primers recognizing conserved sequences of the variable (V), diversity (D) and joining (J) region segments. Association of EBV in AILT cases was studied by PCR and in situ hybridization (ISH). RESULTS This study showed AILT to constitute 0.71% of all NHLs (non-Hodgkin's lymphoma) [both T and B]. Immunohistochemical study revealed that the tumor cells were positive for CD45 (LCA), CD45RO (UCHL1) and CD3. All the 13 cases were largely negative for CD20 (L26), a B-cell marker, except few large scattered cells labelling. DNA extracted from all 13 lymph nodes was amplified using polymerase chain reaction (PCR). PCR technique demonstrated clonal gene rearrangement of the TCR-b, g and IgH regions in 3 (23.1%), 7 (53.8%) and 3 (23.1%) AILT cases, respectively out of 13 cases. Association of EBV was seen in 11 out of 13 cases (84.6%) of AILT by PCR. By ISH the prevalence of EBV was detected in 8 (88.8%) out of 9 cases. CONCLUSIONS The prevalence of AILT in the Pakistani population is slightly lower compared to other studies and that EBV is an etiological agent in pathogenesis of this disease.