Chronic lymphocytic leukemia (CLL) is one of the most common lymphoid malignancies and is characterized by a tremendously variable clinical course. Additionally, whereas the median age at diagnosis is 72 years, CLL is diagnosed with increasing frequency in younger patients. Given the toxicities associated with currently available therapies, being able to predict which patients will need treatment could play a significant role in preserving bone marrow function and reducing morbidity and mortality. While a great many prognostic markers have been identified that predict outcomes for patients with CLL. Learning how to use these prognostic markers to provide patient care is more difficult.