The primary objective of this study is to collect health economic data depicting the initial levels and natural progression over time of resource usage, Parkinson's disease (PD)-related costs, and health related quality of life (HRQoL) for a cohort of advanced PD patients treated with Duodopa (levodopa-carbidopa in an intestinal gel formulation), of which about one-third were Duodopa-naïve prior to the start of the study.