The Leucine-rich repeat kinase 2 (LRRK2) gene has been identified as a disease susceptibility gene for Parkinson's disease (PD), with G2019 (6055G>A) being the most frequent mutation. This mutation was present in 42% (38/91) of Tunisian families and 2% (1/39) of US families we have studied. A founding haplotype was identified in our data and it is shared by families from Tunisia, US, European and Middle Eastern countries. The most recent common founder of the mutation was dated to 2600 (95% CI: 1950-3850) years ago although additional studies are warranted to ensure an accurate age estimate for this mutation.