Mutation in the LRRK2 gene is a known genetic cause of Parkinson disease (PD). However, due to the high frequency in which the most frequent LRRK2 mutation is present and the large size of LRRK2 gene, a complete sequence-based screening of the entire coding region has only been performed by a few researchers. In addition, normal variability in the LRRK2 gene has only been fully assessed in the North American population. Although a complete examination of the entire gene is required to assess the exact contribution of LRRK2 to the etiology of PD, more than 50 variants have been reported to date within the LRRK2 locus. Gene multiplications or deletions have not been reported so far. Here, all LRRK2 variants reported are interpreted and their contribution to the disease is examined. Hum Mutat 30,1–8, 2009. © 2009 Wiley-Liss, Inc.