Inclusion Criteria:  Primary diagnosis of Chronic Lymphocytic Leukemia (CLL)  Initiated CLL treatment (including 1st line, 2nd line, or Subsequent lines of treatment) within the period between 01 June 2016, and 12 months before data collection  - For GCC pilot cohort patients: treatment-naive CLL patients diagnosed between 01 June 2016, and 12 months before data collection.  Available medical records at the participating site reflecting at least 12 months of follow-up after starting on treatment (except in the case of the participant death within one year following treatment initiation). Provision of informed consent by the patient or next of kin/legal representative (for deceased patients at study entry, unless a waiver was granted), according to local regulations. Adult male or female ≥18 years old at the time of diagnosis or according to the age of majority as defined by local regulations).  Exclusion Criteria:  Failure to meet one or more of the inclusion criteria. Any diagnosis of B-cell malignancies other than CLL. Current or prior use of "acalabrutinib" treatment. Currently/previously receiving treatment in an interventional clinical trial at the time of entry into this study for indications CLL.