AbstractOBJECTIVE:To characterize fatigue in Parkinson's disease (PD).BACKGROUND:Fatigue is a recognized problem in PD. Fatigue can be in the physical realm or in the mental realm. Fatigue has not been characterized in PD.METHODS:We characterized fatigue in 39 PD patients and 32 age‐matched normal controls using five questionnaires: A. The Multidimensional Fatigue Inventory (MFI), which measures five dimensions of fatigue independently including general fatigue, physical fatigue, reduced motivation, reduced activity, and mental fatigue. B. The Fatigue Severity Inventory (FSI), which quantifies fatigue in general. C. The Profile of Mood States (POMS), which assesses six subjective subscales: tension‐anxiety, depression‐dejection, anger‐hostility, fatigue‐inertia, vigor‐activity, and confusion‐bewilderment. D. Center for Epidemiological Studies‐Depression Scale (CES‐D). E. Visual Analog linear scale of energy (VA‐E).RESULTS:PD patients scored higher in all of the five dimensions of fatigue in the MFI including general fatigue, physical fatigue, reduced motivation, reduced activity, and mental fatigue (P < 0.001 except for mental fatigue P = 0.005). The severity of physical fatigue did not correlate with that of mental fatigue. PD patients scored higher on the FSI, POMS, CES‐D, and scored lower on the VA‐E. The scores in the FSI correlated with general fatigue, physical fatigue, reduced activity, and reduced motivation but not with mental fatigue in the MFI. Depression correlated with all dimensions of fatigue except physical fatigue in the MFI. Disease severity, as measured by Modified Hoehn and Yahr staging, did not correlate with any of the measures.CONCLUSIONS:PD patients have increased physical fatigue and mental fatigue compared to normals. Physical fatigue and mental fatigue are independent symptoms in PD that need to be assessed and treated separately. © 2001 Movement Disorder Society.