Aim: The first evaluation of the efficacy and safety of ropinirole prolonged release (PR) as an adjunct to L-dopa in Chinese patients with advanced Parkinson's disease (PD) not optimally controlled with L-dopa. Methods: In a 24-week, double-blind, placebo-controlled, parallel-group study, subjects with advanced PD were randomized 1:1 to ropinirole PR (N = 175) or placebo (N = 170) as add-on therapy to L-dopa. Primary outcome measure was change from baseline in awake time spent "off". Starting dose of ropinirole PR was 2 mg/day, titrated based on clinical response (maximum 24 mg/day). Results: At week 24, the mean dose of ropinirole PR was 11.4 mg/day with a mean reduction of L-dopa from 506.6 to 411.6 mg/day. Subjects receiving ropinirole PR experienced a significant reduction of "off" time (2.1 h) compared with placebo (0.4 h). Secondary outcome measures including hours of "on" time without troublesome dyskinesis were significantly increased in the ropinirole PR group (1.7 h) compared with placebo (0.3 h). Subjects classified as responders were significantly more frequent in the ropinirole PR (22.8%) than placebo group (2.5%). Efficacy outcomes including Unified Parkinson's disease Rating Scale and PDQ-39 subscales of mobility were significantly improved in the ropinirole PR versus placebo group. The most frequent adverse event experienced in the ropinirole PR group was dyskinesia. Conclusions: This study demonstrated for the first time in Chinese subjects that ropinirole PR improved Parkinson's disease symptoms, permitting a reduction in L-dopa dose. The adverse events observed were consistent with the established safety profile of ropinirole, with no new safety signal identified. (C) 2013 Elsevier Ltd. All rights reserved.