The aims of the present study were: (i) to describe and compare the characteristics and clinical course of CLL patients according to karyotype complexity detected by CBA, (ii) to analyze the impact of complex karyotype (CK) and high-risk FISH deletions (ATM and/or TP53, HR-FISH) on time to the first therapy and overall survival. This evidence concerns the gene ATM and B-cell chronic lymphocytic leukemia.