The aim of our study was evaluation of the relationship between apolipoprotein E (APO E) genotype and the clinical parameters in Parkinson's disease (PD) with and without dementia. 104 PD patients were evaluated and within this group two subgroups were formed: 51 PD patients (25 males, 26 females; mean age: 70.4 +/- 6.03 years) with dementia and 53 (31 males, 22 females; mean age: 62.5 +/- 8.57 years) without dementia. The estimation of APO E genotype was executed by means of Polymerase Chain Reaction. The Unified Parkinson's Disease Rating Scale was used to quantify the severity of PD. Cognitive functions were assessed according to the Mini Mental State Examination. APO E genotype and allele frequencies did not differ between demented and nondemented parkinsonian patients.