TIA-1 (T-cell intracytoplasmic antigen) monoclonal antibody reacts with a 15 kDa cytoplasmic granule-associated protein, expressed in lymphocytes processing cytolytic potential. The expression of TIA-1 was studied in CD30+ anaplastic large cell lymphomas (ALCL), NK cell lymphomas and peripheral T-cell lymphomas and T cell lymphocytosis, B-cell lymphomas and lymphoblastic leukemia, Hodgkin’s etc. Studies showed that 60 to 70% of anaplastic large cell lymphoma reacted with TIA-1. Studies also indicate that TIA-1 reacts with most large granular lymphocytic leukemia’s, hepatosplenic T-cell lymphomas, intestinal T-cell lymphomas, NK-like T-cell lymphomas, NK-cell lymphomas, nasal T/NK-cell lymphomas, subcutaneous T-cell lymphomas, pulmonary angiocentric lymphomas of T or NK phenotype. The author’s concluded from TIA-1 studies that anaplastic large-cell lymphomas are cytotoxic T-or NK-cell neoplasms. All B-cell lymphomas, Hodgkin’s and lymphoblastic leukemias were negative for TIA-1.