 This 2 stage study will compare the pharmacokinetics and safety profile of subcutaneous and intravenous rituximab in participants with follicular lymphoma. In the first stage, participants who have achieved at least a partial response after induction treatment with intravenous rituximab will be randomized to one of 3 treatment cohorts, to receive rituximab 375 milligram per square meter mgm2 intravenously, 375 mgm2 subcutaneously or 625 mgm2 subcutaneously, and pharmacokinetics evaluated on an ongoing basis. Upon selection of the subcutaneous dose 800 mgm2 which results in rituximab trough plasma concentration C trough values comparable to those achieved with the intravenous formulation, participants in the second stage of the study will be randomized to receive either the subcutaneous or intravenous formulation to demonstrate comparability of the C trough levels with both routes of administration. Maintenance therapy will continue every 2 or 3 months with the subcutaneous formulation. 