According to the classification of chronic lymphocytic leukemia (CLL) proposed by A. I. Vorob'ev and M. D. Brilliant in 1983, benign CLL is a distinct form of CLL which is characterized by low level of absolute lymphocytosis, absent or mild peripheral lymphadenopathy, slow progression. No specific therapy is needed. The paper presents clinical, morphological and immunological analysis of 34 cases of benign CLL (17 males and 17 females, mean age 58 years). Patients were included in the study if they had lymphocyte count less than 30,000 and no significant growth of lymphoid tissue for at least 3 years. They were followed up from 3 to 24 years (11 years, on the average). The main features of benign CLL are the following: no "B" symptoms, no essential enlargement of the lymphoid organs, a stable low level of absolute lymphocytosis, low prolymphocyte count in the blood smear (0.95% +/- 0.2), nodular or nodular-interstitial proliferation in the bone marrow. We failed to find any cases with paraprotein secretion. There was immunophenotype typical for CLL in 91% of cases (CD19+, CD20+, CD23+, CD5+, EM+, CR1-/CR2+, sIg+(-)). None was positive for CD38 activation marker. One trisomy 12 cases was detected by FISH method. 8 patients died so far, but not because of the tumor progression or transformation, median survival was 22 years.