Cortical evoked responses after single or repetitive stimulations of the nucleus ventralis lateralis (VL), n. centrum medianum (CM) and n. ventralis anterior (VA) were observed in 61 cases of parkinsonism, 7 cases of intractable pain and a case of dystonia musculorum deformans from February, 1968 to December, 1969. Experimental studies of the thalamic stimulations with 15 cats were performed as well and the results were compared with that of the human. Evoked responses were analysed with averaging computer technique. Results were as followings. 1) Cortical evoked potentials after single stimulation of the VL nucleus of the human thalamus. a) Evoked potentials appeared on the ipsilateral centro-frontal regions with weaker stimulation in EEG records. However, the evoked potentials showed clear bilateral distribution except the temporal region, predominantly on both centro-frontal regions, with stronger stimulation electroencephalogaphically. b) The evoked potentials of the central site showed clear three negative waves within 200 msec after the stimulation, that is, the first negative wave (Ⅰ-N) with the peak time of about 10 msec, the second (positive-) negative wave (Ⅱ-PN) with the peak time of about 50 msec and the third negative wave (Ⅲ-N) with that of 80-100 msec with averaging computer records. The peak time of the Ⅰ-N wave and the negative phase of the Ⅱ-PN wave were nearly constant, but that of the Ⅲ-N wave considerably varied according to the background activities of EEG. The evoked potentials showed no significant discrepancy between right and left patterns, and moreover, they maintained a similar pattern when the stimulating voltages were changed. c) Bilateral evoked potentials were clearly seen with averaging computer technique even when evoked potentials were small and hardly identified on the contralateral scalp with EEG records. When the stimulating voltages were gradually decreased, the ipsilateral and contralateral evoked potentials disappeared approximately at the same time. d) The latency of the Ⅰ-N wave was measured to be 5-6 msec with averaging computer records, and the amplitude of the Ⅰ-N wave increased proportionately with the increase of stimulating voltages.