Several pathogenic mutations in the leucine-rich repeat kinase 2 (LRRK2; PARK8) gene recently have been identified in familial and sporadic parkinsonism. We screened 435 Norwegian patients diagnosed with Parkinson's disease and 519 control subjects for the presence of 7 LRRK2 mutations. Nine patients from seven families were found to be heterozygote carriers of the LRRK2 6055G>A (G2019S) mutation. Twelve of 28 first-degree relatives also carried the mutation, but only 1 had Parkinson's disease. The clinical features included asymmetric resting tremor, bradykinesia, and rigidity with a good response to levodopa and could not be distinguished from idiopathic Parkinson's disease. Ann Neurol 2005;57:762–765