A 54-year-old woman presented with a severe autoimmune anemia, thrombocytopenia, neutropenia (Evans' syndrome), and CD8+ lymphocytosis, without signs of lymphadenopathy or splenomegaly. A diagnosis of T cell large granular lymphocyte (T-LGL) leukemia was made, based on cytomorphology, the typical CD3+/CD4-/CD8+/CD16+/CD56-/CD57-/HLA-DR(+/-) immunophenotype of the lymphocytosis (9 x 10(9)/l), and biallelic clonally rearranged T cell receptor beta (TCR beta) genes. Clonality of the TCR alphabeta+ T-LGL was also demonstrated with a panel of antibodies against variable domains of TCR beta chains, which showed single Vbeta7.1 expression on the CD3+ T-lymphocytes. After treatment failure with corticosteroids, splenectomy, and cyclophosphamide, respectively, a complete clinical remission was induced and sustained with cyclosporin A. Vbeta7.1/CD8/CD3 triple immunofluorescence stainings appeared to be valuable for titrating the cyclosporin A dosage by monitoring the T-LGL cells during treatment.