Adult T cell leukemia/lymphoma (ATLL) is a mature T cell malignancy, especially derived from the CD4 positive T cell. To characterize the T cell, we examined the representation of T cell antigen receptor variable region, using the monoclonal antibodies [beta V 5 (a), beta V 5 (b), beta V 6 (a), beta V 8 (a), beta V 12 (a), alpha V 2 (a), alpha-beta V (a)]. Clinicopathologically we classified the lymph nodes of patients with ATLL into three states (1) human T cell leukemia virus type I (HTLV-I) associated lymphadenitis, reactive state; (2) incipient ATLL, early or pre-neoplastic state; and (3) ATLL, neoplastic state. The lymph nodes of all three states were composed of unvarying CD4 positive T cells. Most of the lymph nodes with ATLL consistently presented alpha V 2 antigen, but no others. In HTLV-I associated lymphadenitis, only a few cells reacted for alpha V 2, as in non-specific lymphadenitis without ATLL features. One of three cases with incipient ATLL presented alpha V 2. The selected expression of T cell antigen receptor V region might be associated with the presence of HTLV-I encoded superantigen, similar to human immunodeficiency virus (HIV).