Flow cytometry plays an essential role in the diagnosis and immunophenotypic characterization of T-cell lymphoproliferative disorders. However, the interpretation of flow cytometric findings in T-cell populations is often challenging, given the frequent immunophenotypic overlap between reactive T-cell subsets and T-cell neoplasias. Recently, a previously developed anti-TCR antibody (clone JOVI.1) was shown to recognize only one of two mutually exclusive TCR constant β regions (TRBC1), randomly selected in the process of TCR gene rearrangement. This single anti-TRBC1 antibody can be routinely used in flow cytometry immunophenotyping assays to provide a low-cost, robust and highly specific test that detects clonality of immunophenotypically distinct T-cell populations. Moreover, this strategy virtually eliminates the need for a complex TCR Vβ repertoire analysis by flow cytometry, or a separate molecular T-cell clonality testing in the evaluation of TCRαβ+ T-cell lymphoproliferative disorders. We have recently demonstrated the clinical utility of TRBC1 staining in the diagnostic evaluation of several T-cell neoplasms, including T-cell large granular lymphocytic leukemia, cutaneous T-cell lymphoma, T lymphoblastic leukemia/lymphoma, and peripheral T-cell lymphomas. Some of the requirements for appropriate clinical implementation include optimal dynamic range of TRBC1 staining, careful gating of immunophenotypically distinct T-cell subsets, and recognition of small benign T-cell clones in reactive settings.