Cell surface markers of 44 cases of non-Hodgkin's lymphoma (NHL) were studied with various surface markers, especially by using antihuman B lymphocyte serum (ABS), antihuman thymocyte serum (ATS-T), and antihuman peripheral T lymphocyte serum (ALS-T), which were rendered specific for human B lymphocytes, human thymocytes, and human peripheral T lymphocytes, respectively. An immunofluorescent study with ABS, ATS-T, and ALS-T enabled us to demonstrate the histologic localization of normal or neoplastic B and T cells in preserving the original structure of lymphoid organs or tumor tissues. The proportion of cell types in NHL was B cell type 59%, T1 (ATS-T reactive) type 7%, T2 (ALS-T reactive) type 23%, and Null (non T, non B) type 11%. The relationships among cell types, histologic findings, and clinical characteristics were also investigated. Patients with T1-NHL had mediastinal tumors, which were histologically classified into "Lymphoblastic lymphoma." These facts suggest that T1-NHL may have originated in the thymus. Patients with T2-NHL showed a high incidence of skin lesions. Median survival of ten patients with T1- and T2-NHL was seven months, which was much shorter than that of B- or Null-NHL.