Chronic lymphocytic leukemia (CLL) is dramatically increased in patients above the age of 65 years up to an incidence rate of 22-30/100 000. Although elderly patients represent the largest group of CLL patients they are clearly underrepresented in clinical trials. One important prognostic factor in the elderly is the burden of comorbidity. Survival is significantly impaired in CLL patients with multiple comorbidities (>or=2) or with severe comorbidity (Charlson score >or=2). Therefore, not only age but also the incidence and burden of comorbidity should influence the choice of treatment strategy for every patient individually. A reliable tool for measuring comorbidity is the Cumulative Illness Rating Scale. The German CLL Study Group (GCLLSG) has used this tool within their clinical trials to distinguish between physically fit and non-fit patients. Although chlorambucil is still the standard treatment of choice in non-fit patients, dose-reduced purine analogue-based combination therapies with or without immunotherapy are currently investigated within clinical trials. Because full-dosed combination treatment might cause increased toxicity rates in relapse situation, dose-reduced combination therapies should be considered in this situation. An adequate supportive treatment is necessary for the prevention of toxicities as well as for the improvement of health-related quality of life. In summary, the treatment decision in elderly CLL patients is carefully to be made in each patient individually considering not only the stage and risk factors of the disease but also the patients' physical condition and social environment.