In the analysis of the mutation related to NOTCH1, exon 34, PEST domain and SF3B1, exons 14–16, HEAT domain repeats 3–6; it was found that out of 51 patients, 32 patients (62.74%) with CLL phenotype, 18 patients (35.29%) with aCLL phenotype, and one patient (1.96%) with PLL phenotype were evaluated. The gene discussed is NOTCH1; the disease is B-cell chronic lymphocytic leukemia.