The extensive involvement of NFAT transcription factors in the induction of T cell anergy18, 20 and the overexpression of NFAT2 in CLL23, 24 prompted us to investigate its precise function in this disease using the Eμ-TCL1 transgenic mouse model and primary human tissue samples from patients with CLL and Richter’s syndrome. This evidence concerns the gene NFATC1 and B-cell chronic lymphocytic leukemia.