The dopamine D4 receptor (D4DR) has a highly polymorphic region in the third exon which has been associated with novelty seeking (NS) behavior. Due to the central position of dopamine and the documented low NS in Parkinson's disease (PD), the frequency of the exon 3 variants of D4DR in 95 PD patients and 47 controls was investigated. A significantly higher frequency of exon 3 alleles with six or more repeat units was found in the PD group (p = 0.039). This provides evidence that some forms of the highly polymorphic D4DR may represent a genetic susceptibility factor for PD.