Background and purposePortugal has been identified as one of the countries with a high prevalence of LRRK2-G2019S, considered to be the most frequent known cause of familial and sporadic Parkinson's disease (PD). The aim of this study was to evaluate the prevalence of PD in Portugal using a door-to-door methodology. MethodsA cross-sectional study was conducted in the Portuguese community-dwelling population; that is, elderly people living in the community on their own, aged 50years and resident in mainland Portugal, in two phases: (i) a questionnaire was applied to screen potential cases of PD; and (ii) screened cases were evaluated by an expert in PD to confirm diagnosis. ResultsThe adjusted prevalence of PD for the Portuguese community-dwelling population aged 50years was 0.24%. The estimated total number of cases of PD for the Portuguese population is 180/100000 inhabitants. ConclusionsThe results of this study show that a geographical region with a high frequency of a causal mutation for PD does not automatically imply a high prevalence of patients with PD.