One- and two-dimensional polyacrylamide gel electrophoresis (PAGE) was performed on immunoprecipitates formed between anti-human T-cell xeno-antiserum (ATS) and cell-surface glycoproteins of human lymphocytes, that had been radioiodinated by lactoperoxidase and purified on a Lentil lectin-coupled Sepharose 4B column. In some experiments, the cells were 3H-labeled by periodate-tritiated borohydride. ATS that was absorbed with B cells recognized a number of cell-surface antigens expressed preferentially on human thymus and T cells, with molecular weights of 150K (T150), 94K (T94), 72K (T72), and 65K (T65) daltons. Whereas T150 appeared to consist of multiple components of heavily sialylated glycoproteins and to be expressed largely on thymus and T cells, and to a much lesser extent on B cells, the remaining T94, T72, and T65 glycoproteins seemed to be present on thymus and T cells but absent from B cells. Two-dimensional PAGE analysis of these T-cell glycoproteins precipitated by ATS demonstrated that T94 was an acidic glycoprotein with pI of 4, while T72 and T65, the latter being found on thymus and T cells but not on T cell-type leukemic cells, exhibited marked electric charge heterogeneity with pI ranging from 4 to 7. These data clearly suggest that human thymus and T cells possess a complex antigenic make-up on their cell surfaces, comparable to that of mouse T cells with a variety of Ly antigen systems.