A monoclonal antibody (mAb) with framework reactivity against the T cell receptor (TCR) alpha beta complex is characterized. The mAb, beta Framework 1 (beta F1) is capable of immunoprecipitating the TCR alpha beta complex from 125I-labeled human T cell tumors, immunocompetent T cell clones, and peripheral blood lymphocytes (PBL). beta F1 recognizes the separated TCR beta subunit in Western blotting. Because it does not bind to the surface of viable T cells but does react with the plasma membrane form of the TCR after treatment with membrane solubilizing agents, the beta F1 mAb reacts with a "hidden" determinant on the TCR beta subunit. After solubilization with 70% ethanol, the TCR alpha beta complex is shown to exist on greater than 92% of T3+ human PBL, whereas 2 to 8% of T3+ PBL do not react with the mAb. The beta F1 mAb demonstrates the existence of differently glycosylated surface 125I-labeled TCR alpha-chains (alpha, alpha', alpha") in association with a common TCR beta-chain on the HPB-MLT T cell leukemia. Reactivity of the beta F1 mAb on thymus tissue sections is similar to that of anti-Leu-4 (anti-T3). The beta F1 mAb should prove useful as a research tool for both the immunochemical characterization and isolation of virtually any alpha beta T cell receptor, whether from individual T cell clones or polyclonal populations of T lymphocytes. Recognition of T cell receptors in histologic tissue sections suggests that the beta F1 mAb may be useful in the clinical diagnosis of T cell lineage neoplasms. In failing to recognize all T3+ lymphocytes, it allows the identification of novel populations of T3+ lymphocytes that may express non-alpha, non-beta T cell receptors.