This single arm, multicenter study will evaluate the safety, efficacy and pharmacokinetic (PK) of subcutaneous (SC) rituximab in previously untreated participants with cluster of differentiation 20 positive (CD20+) DLBCL or FL. In addition to standard chemotherapy, participants will receive at least 4 doses of rituximab 1400 mg SC once a month during the Induction period, and at least 6 doses of rituximab 1400 mg SC once every two months during the Maintenance period.