The combination of entacapone with levodopa is effective in the treatment of Parkinson's disease (PD), providing significant improvements in 'on' time and Unified Parkinson's Disease Rating Scale (UPDRS) motor and ADL scores in controlled clinical trials. This multicentre, open-label study was designed to further evaluate the effectiveness of levodopa combined with entacapone 200 mg in routine clinical practice. Patients experiencing end-of-dose wearing-off were treated for 8 weeks (treatment phase), with an optional extension phase up to 20 weeks. The primary efficacy parameter was the Investigators' Global Assessment of Change; secondary efficacy parameters included UPDRS, 'off' time (from patient diaries), Patients' Global Assessment of Change, quality of life (QoL), SF-36 Health Assessment Questionnaire and Parkinson's Disease Questionnaire 39 (PDQ-39). Of the 479 patients who entered this study, 427 (89.1%) completed the treatment phase and 374 (78.1%) continued into the extension phase. Based on the Investigators' Assessment of Change, 380 (79.7%) patients showed an improvement with entacapone during the treatment phase. This improvement was maintained into the extension phase, and at Week 20, 301 (82.2%) patients continued to show an improvement. A positive treatment effect with entacapone was also seen with all secondary efficacy parameters, including QoL. Mean change in the total PDQ-39 scores showed improvements from baseline of -4.0 score points to the end of the treatment phase (n=182) and -3.1 score points at the end of the extension phase (n=152). Entacapone in combination with levodopa was generally well tolerated: 40 patients (8.4%) discontinued treatment due to adverse events (AEs) by the end of the extension phase. This study in a daily clinical practice setting confirmed the efficacy of coadministering entacapone with levodopa shown in controlled clinical trials and suggests that the combination is useful in improving the disability and QoL in patients with PD.