In dipole localization analysis, the problems of accuracy of the estimated source and reliability of multiple dipole analysis remain to be elucidated.We performed dipole estimation of SEP components which were yielded in 10 subjects using both single-layer and 3-layer models, to investigate difference of the estimated sources between the two models. We also carried out 2-dipole model analysis of SEP components by simultaneous stimulation of the bilateral median nerves to evaluated the usefulness of the 2-dipole model analysis.Conclusion: (1) By the 3-layer models, the N20 sources were estimated to locate appropriately at the position which corresponded to the hand somatosensory representation area on the postcentral gyrus in MRI. By the single-layer model, on the contrary, the estimated source positions were deep in the brain near the thalamus in MRI.(2) The dipoles which were longitudinally estimated for SEPs from the latency 18 msec to 40 msec, had almost the same positions with rotating orientations in both models, suggesting that both generators of P25 and N35 were in the vicinity of that of N20.(3) The 2-dipole analysis yielded bilateral symmetric dipoles for the SEP components which were brought about by bilateral stimulation.