Chronic lymphocytic leukaemia is the most frequent form of malignant hematological diseases in the Western countries, it comprises 30-40% of all the leukaemias and it manifests itself between 60-65 years of age. Clinical features are caused in 93% of the cases by the accumulation and proliferation of immunologically incompetent, anergic, long lived, CD5 positive B-lymphocytes, expressing monoclonal IgM or IgD immunglobulin, in the bone marrow, the peripheral blood, the lymphoid and in other organs. In the etiology genetic basis is highly supposed, whereas affect of toxic agents and radiation exposure can be neglected. The prognosis of patients is variable and is determined by the clinical stage and the proliferative activity of the disease. Treatment is indicated in intermediate and high-risk clinical stages only with signs of disease activation on the basis of individual patient's risk. As first line treatment, Chlorambucil is indicated in high doses. Results achieved by combined chemotherapy are generally not superior compared to high-dose Chlorambucil treatment. For patients who developed resistance to alkilating agents purin analogues are recommended. Out of them the most favorable results had been accumulated with Fludarabine as second line treatment. For minority of the cases hemopoetic stem cell transplantation as the only curative therapeutic measure is being introduced in an increasing number. This review gives an account of the recent advances in the diagnosis and therapy of the disease.