Technologies that allow genotyping of more than 100,000 polymorphisms in a single assay enable the execution of genomewide SNP (GWSNP) association studies to identify common genetic variants underlying traits. Less appreciated is the ability of GWSNP assays to map and directly identify rare mutations that cause disease. Here we show the use of this approach in identifying rare structural mutations involved in disease using a large cohort of Parkinson disease (PD) patients and neurologically normal controls by examination of genotype data and copy number metrics. This approach revealed a patient with homozygous mutation at the PARK2 locus. In addition, two heterozygous deletion mutations and five heterozygous duplication mutations within PARK2 were identified in PD subjects and controls. All mutations were confirmed by independent gene dosage experiments. These data demonstrate the utility of this approach in the direct detection of mutations that underlie disease. Hum Mutat 29(2), 315–322, 2008. Published 2007 Wiley-Liss, Inc.