Relevance. The high prevalence of chronic lymphocytic leukemia (CLL) in elderly and senile patients of the European population dictates the need to find a publicly available solution to the problem of prognosis in this cohort of patients. Previously, a relationship was established between the survival of patients with CLL and the value of the glomerular filtration rate (GFR) at the time of diagnosis. The purpose of the study: to assess the relationship of GFR with the survival of CLL patients in the course of the disease. Materials and methods: 207 patients (98 men and 109 women) aged 45 to 80 years with CLL A-C according to Binet and known overall survival were studied. Annually from the 1st to the 5th year of the course of the disease, the maximum value of the patient's GFR was taken into account according to the CKD-EPI formula. The data was processed by data mining using a logical classification algorithm. Results. With a GFR value of more than 76 ml/min/1.73 m2 during the first year of the disease, more than 75 ml/min/1.73 m2 during the second year of the disease, more than 70 ml/min/1.73 m2 during the third year of the disease, more than 68 ml/min/1.73 m2 during the fourth and fifth years of the disease, the patient will overcome the calculated parameters of the median survival for the corresponding stage of CLL according to Binet. Otherwise, the overall survival of the patient will be less than the calculated median survival according to Binet. This article provides illustrative clinical examples. Conclusion. It was found that the value of GFR in CLL patients gradually decreases with the course of the disease, however, the value of this parameter in the dynamics of the disease can be considered as a significant factor in predicting the survival of patients with CLL. Based on the results, an application for an invention No. 2023108368 was filed.