A 72-year-old Japanese man presented with CD4+ T cell receptor (TCR) gammadelta T cell lymphoma involving bilateral cervical lymph nodes. No involvement by tumor was observed in the liver, spleen, nasal cavity, or bone marrow throughout his clinical course. Although the tumor adequately responded to chemotherapy and irradiation, he relapsed with short remission and a slowly aggressive clinical course, and died 24 months after onset. Simultaneous expression of TCR gammadelta with other T-cell antigens on the lymphoma cells was analyzed by 3-color flow cytometry (3-FCM), and showed a unique phenotype CD3+ CD4+ CD8- CD7- CD5+ CD2++ TCR alphabeta (WT31)- betaF1-TCR gammadelta1 (11F2)+ TCR delta1+. Cytogenetic analysis showed 79-81 and structural abnormalities consisting of del(1)(p11) and i(17)(q10). But no abnormality was identified in chromosome 7. DNA analysis revealed gene rearrangements of TCRgamma and delta, while a nongerm line band in TCRbeta was aberrantly seen. These observations suggest a new subtype of gammadelta T-cell lymphoma, which is characterized by CD4 positivity and by a clinical course not as aggressive as other predominant subtypes.