The objective of this multicenter cross-sectional study was to determine the prevalence of fatigue and factors contributing to it in a large sample of Japanese patients with Parkinson's disease (PD). We used the 16-item Parkinson Fatigue Scale (PFS-16), which was designed to assess fatigue exclusively associated with PD. We carried out this study using PFS-16, the Unified Parkinson's Disease Rating Scale, Zung's Self-Rating Depression Scale, Parkinson's Disease Sleep Scale (PDSS), and the PD quality of life (QOL) scale (PDQ-39) by interview using questionnaires and physical examination by neurologists in 361 nondemented PD patients. Fatigue (an average PFS score of 3.3 or greater) was revealed in 151 patients (41.8%). Multiple logistic regression analysis indicated that the significant independent variables related to the presence of fatigue were the scores of PDSS and PDQ-39. Depression score was not a significant contributing factor. Our study revealed that the prevalence of fatigue in Japanese PD patients is as high as that in Western countries, and that fatigue is a relatively independent symptom, although sleep disturbance may be associated with fatigue. Since fatigue is significantly related to QOL reduction, therapeutic interventions including treatment of sleep disturbance are important.