Summary:The object of the present study was to evaluate the hand tremor occurring under various conditions in 81 patients with Parkinson's disease (PD) and to statistically analyze their relation to clinical rating items. We found that resting and action tremor have to be separated, whereas postural tremor can be related to either one of them. Resting tremor does not correlate with disability items or performance items except for an item rating social handicaps. Action tremor shows some influence on performance items. Current rating scales of PD represent a valid measure of resting tremor but are less valid for the measurement of action tremor.