Study S187.3.001 (NCT00357994) and Study S187.3.002 (NCT00660387) were 2 identically designed, Phase 3, 12-week, randomized, double-blind, double-dummy, parallel-group, multicenter studies recruiting subjects from distinct sites. These studies evaluated the efficacy, safety, and tolerability of levodopa-carbidopa intestinal gel (LCIG) in the treatment of levodopa-responsive subjects with advanced PD who had persistent severe motor fluctuations, despite optimized treatment with oral levodopa-carbidopa, concomitant with other available antiparkinsonian medications. Participants were randomized to either LCIG active gel + placebo capsules or levodopa-carbidopa immediate release (IR) active capsules + placebo gel. Both treatment arms received the percutaneous endoscopic gastrostomy with jejunal extension (PEG-J) procedure for gel administration, active LCIG or placebo gel. Data from these 2 studies were combined for analysis. The decision to combine the study data for analysis was made before enrollment was completed for both studies.