Age over 18 years

Previously untreated, relapsed or refractory CD 20-positive FL

Responding to rituximab containing induction therapy (complete response \[CR\] or partial response \[PR\])

To receive rituximab maintenance therapy (decision taken by doctor prior to and independent of this non-interventional study)

No ineligibility for rituximab

Non-Interventional Study to Examine Rituximab Treatment in Follicular Lymphoma Participants