The aim of this work was to examine the segmental motoneuron activity as a possible mechanism of tremor generation. Eighty-three patients with different types of tremor (25 with Parkinsonian, 29 with essential, and 30 with enhanced physiological tremor due to anxiety), 25 Parkinsonian patients without tremor and 30 healthy volunteers were examined. The tremor was studied clinically and by electromyography in all limb positions. The F wave was examined for assessment of motoneuron activity. The wave was recorded after stimulation of the ulnar, median, tibial and fibular nerves. The maximal and mean F wave amplitudes, frequency of occurrence and number of phases were increased, and the duration was prolonged in all group of patients as compared to the healthy persons. The maximal and the mean F/M amplitude ratios, as well as the Fmean./Fmax amplitude ratio were increased in all groups of patients. All F wave parameters were most altered in Parkinsonian tremor patients followed by patients with rigidity. In conclusion increased motoneuron activity participates in generation of different types of tremor and in Parkinsonian rigidity.