Aim. To evaluate the efficiency and safety of monotherapy with bendamustine (B) and therapy with B in combination with rituximab (B + R) in patients with chronic lymphocytic leukemia (CLL) accompanied by renal failure (RF). Subjects and methods. The prospective pilot study included 8 patients (6 men, 2 women) with CLL concurrent with RF. The patients' median age was 63 years (51-77 years). The Binet classification stage of CLL corresponded to B in 2 cases and C in 6. The mean (± standard error) pretreatment concentration of creatinine was 218±92 µmol/l and the glomerular filtration rate (GFR) was 33±20 ml/min. The efficiency of monotherapy with B (n=5) and combination therapy with B + R (n=3) was evaluated. In progressive CLL, therapy was performed in specific treatment-naïve patients (n=5) and in pretreated patients refractory to alkylating agents (cyclophosphan, chlorambucil) (n=3). A total of cycles of B and B + R were carried out. Results. After B monotherapy, one of the 5 cases achieved a complete remission, 3 a partial remission, and 1 a nodular partial remission. Three patients developed recurrence. In the B monotherapy group, the cumulative risk of recurrence was 70% at a median follow-up of 22 months and at a maximum follow-up of 27 months. In the B + R therapy group, all the 3 patients achieved a complete remission. The median follow-up was 7 months; the maximum follow-up was 1 year. There were no deaths or recurrences. During B monotherapy and B + R combination therapy, there was improved kidney function: the mean concentration of creatinine decreased from 218±92 to 140±57 µmol/l (p<0.05); GFR increased from 33±20.0 to 54±25 ml/min; the mean increment was 20 ml/min (p<0.01). Mild and moderate anemia and thrombocytopenia were most common during B and B + R therapies. Neutropenia with mild infection complications, as well as nonhematologic complications were detected in some cases. The drugs were observed to have no nephrotoxic effects. Conclusion. The performed pilot prospective indicated that the B + R combination therapy was effective in patients with RF-associated CLL. No toxic effect of B on kidney function was seen. During B therapy, there was better kidney function manifesting itself as a statistically and clinically important decrease in creatinine concentrations and a statistically and clinically important increase in GFR as compared to the baseline values.