The authors investigated the distribution of interleukin-2 receptors (TAC antigen) in the lymph nodes of 300 patients with lymphoproliferative disorders. They used fresh-frozen sections to evaluate a possible correlation between the immunophenotype of specific lymphoid disorders and the presence or absence of TAC expression and to determine whether the TAC positivity of lymphoid cells contributes to the characterization of lymphoproliferative processes. All of the cases had previously been studied with a large screening panel of monoclonal antibodies and polyclonal antisera. Among 85 patients with a variety of benign reactive processes, the lymph nodes from 47 contained TAC-bearing lymphocytes in various patterns of distribution. Of 41 patients with Hodgkin's disease, 37 had TAC-bearing lymphocytes. Of 26 B-cell, well-differentiated lymphocytic lymphomas (WDL), 14 were diffusely TAC-positive and one had TAC-bearing cells in random distribution. Six cases of intermediate lymphocytic lymphoma were also studied, and three showed randomly distributed TAC-bearing lymphocytes. Of 19 patients with follicular or follicular and diffuse, poorly differentiated lymphocytic (PDL) lymphoma, 14 were TAC-positive. All 3 diffuse PDL lymphomas studied were TAC-negative. Among 23 cases of B-cell and 5 cases of T-cell mixed cell lymphoma, 15 and three, respectively, had TAC-positive lymphocytes. Of 39 large cell lymphomas (B-cell, 33; T-cell, 6), 14 were TAC-positive. All 13 cases of hairy cell leukemia were diffusely positive. Of 23 T-lymphoblastic lymphomas, only 1 showed positive TAC reactivity, which was focal. Of 5 cases of cutaneous T-cell lymphoma, 2 had TAC-bearing lymphocytes. Our study indicates that the TAC antigen is not lineage-specific, and that it may be expressed by lymphoid cells regardless of their phenotype.