The efficacy of entacapone and its impact on patient quality of life (QOL) was investigated in an open-label study of 899 patients with idiopathic Parkinson's Disease (PD) experiencing wearing-off fluctuations. Patients were divided into 3 groups (3, 4 or 5 doses daily) based on their current levodopa dosage frequency. Patients received 200 mg entacapone with each levodopa/dopa-decarboxylase inhibitor (DDCI) dose, while continuing their same levodopa/DDCI dosage regimen for 4 weeks. Primary efficacy measure was the Investigators' Clinical Global Impression of Change (CGIC). Patient QoL was assessed using the validated 8-item Parkinson's Disease Questionnaire (PDQ-8). Investigators' CGIC revealed that 76.5% of entacapone treated patients experienced an improvement in global status after 4 weeks. Treatment with entacapone was also associated with improvement in patient QoL, with a mean reduction (improvement) in PDQ-8 score of 1.8 from baseline. This study confirms and extends the results of earlier studies demonstrating that, independent of dosing frequency, completing levodopa/DDCI therapy with entacapone provides clinically relevant improvements in global status and QoL in PD patients experiencing wearing-off on their current levodopa dosing frequency.