Most cases of Chronic lymphocytic leukemia (CLL) remain an incurable disease with the goal of therapy being to improve quality of life and to prolong survival. This study will evaluate the participant's related outcomes and experience of CLL in adult participants who are treated in the Japan.

Study participants will receive oral treatments of Venetoclax±Rituximab for CLL as prescribed by their study doctor in accordance with approved local label. Adult participants prescribed various treatments Venetoclax±Rituximab will be enrolled. Around 89 participants will be enrolled in the study in sites in Japan.

Participants will receive oral venetoclax tablets ± intravenously (IV) infused rituximab treatments for CLL according to the approved local label. The overall study duration will be 27 months.

There is expected to be no additional burden for participants in this trial. All study visits will occur during routine clinical practice.

Inclusion Criteria:

• Diagnosed with relapsed/refractory (2 Line [2L]+) chronic lymphocytic leukemia (CLL) in Japan based on International Workshop on Chronic Lymphocytic Leukemia (iwCLL) criteria at the time of informed consent (IC).
• Treatment with Venetoclax±Rituximab for 24 months who are not treated with any other concurrent CLL treatment.
• Expected to visit the hospital at + 3 months after treatment with Venetoclax±Rituximab for 24 months.

Exclusion Criteria:

• No data on information on the start and end dates or continuation of treatment with Venetoclax.
• Participating in other clinical trials.

Adult participants diagnosed with chronic lymphocytic leukemia (CLL) treated with Venetoclax±Rituximab and attend to a regular follow up visit at a Japanese participating hospital will be eligible to participate in the study.