Brief Summary:

Chronic lymphocytic leukemia (CLL), a form of Non-Hodgkin's Lymphoma, is the most common type of leukemia in adults, affecting approximately 3,800 people in the UK each year. This study will evaluate the patient experience of CLL in adult participants who are prescribed venetoclax+rituximab or Bruton's tyrosine kinase inhibitors in the United Kingdom (UK). Venetoclax+rituximab is a drug approved to treat CLL. Study participants will receive venetoclax+rituximab as prescribed by their study doctor in accordance with approved local label. Adult participants prescribed venetoclax+rituximab or Bruton's tyrosine kinase inhibitors will be enrolled. Around 140 participants will be enrolled in the study in approximately 10 sites in the UK. Participants will receive venetoclax tablets to be taken by mouth and rituximab intravenous (IV) injection according to the approved local label. There is expected to be no additional burden for participants in this trial. All study visits will occur during routine clinical practice.