Thalamic evoked potential (TEP) was recorded in VPM-VPL nuclei following ulnar and sciatic stimulation in humans. The latencies of the early positive deflection were found respectively at 9.6±1.5 and 21.2±3.1 msec for stimulation at the elbow and at the popliteal fossa. It was proved that TEP is not produced by muscular activity and is unaffected by attention or distraction. Stimulation of low threshold afferent fibers of the ulnar nerve was followed by TEP, even in the absence of EMG responses. Their nature is discussed. No clear evidence was found that group I afferent fibers of the sciatic nerve project to the thalamus. Group II cutaneous fibers project to the thalamus also through a fast route; late components of TEP (40–45 msec for the ulnar nerve stimulation) are assigned to group III excitation.