OBJECTIVE To develop a new method for REZ-1 cochlear implant electrode array insertion. METHODS REZ-1 cochlear implant electrode array was implanted in 22 human temporal bone specimens. Cochlear diameters were measured from spiral CT scan before implantation. Cochlear views were taken before and after pullback technique. Modiolus-electrode distances were measured and compared. The diameters of sixty normal cochleae were measured. RESULTS In 3 cases, 27 electrode rings were inserted into the cochlea, while in others, all 28 electrode rings were inserted into the cochlea. After pullback of the electrode array, No. 12 to No. 19 electrode rings were closer to the modiolus in 17 cases (paired t test, P<0.01). The cochlear diameters in the 17 cases were smaller than 9.50 mm, while in the other 5 cases, the cochlear diameters were at least 9.60 mm. The cochlear diameters in the 17 cases were 9.11 (0.57) mm, while the cochlear diameters in the 5 cases were 9.78 (0.28) mm (Mann-Whitney test, P<0.001). The diameters of normal cochleae were (9.04 +/- 0.45) mm, with 90% larger than 9.50 mm. CONCLUSIONS In cases whose cochlear diameter is smaller than 9.50 mm, pullback technique can help some electrode rings be closer to the modiolus. Measurement of the cochlear diameter can help the surgeon to have a better choice in the selection of REZ-1 cochlear implantation methods.