AbstractParkinson's disease (PD) is a common progressive neurodegenerative disorder characterized clinically by a combination of motor symptoms. Identifying novel PD genetic risk factors is important for understanding its pathogenesis. A recent study suggested that up to 21% of subjects with PD may have mutations in the glucocerebrosidase (GBA) gene. We investigated the GBA gene for mutations in 88 PD cases and 122 normal controls and detected the presence of heterozygous GBA mutations in 5 PD cases and in 1 control. Sequencing of the entire open reading frame of the GBA gene in a subset of 25 cases with early‐onset PD (<50 years of age) uncovered no additional mutations. Our results demonstrate a marginally significant association of GBA mutations with PD and suggest that variations in the GBA gene may constitute a rare susceptibility factor for PD (P = 0.048). © 2004 Movement Disorder Society