PURPOSE: Purpose :To evaluate the position and transverse dimension of the adult optic chiasm in normal Korean adult. MATERIALS AND METHODS: The authors analysed 3D coronal volume images (TR/TE= 30/13, flip angle= 30 °) of 136 normal adult subjects without known visual abnormality. All MRI examinations were performed using a 0.5T system. MRI was reviewed retrospectively to determine the position (horizontal and tilted) of the potic chiosm and the transverse dimension of the optic chiasm was measured. RESULTS: Seventy-five (55%) of 136 normal subjects had horizontal position, and sixty-one (45%) had tilted position. Thirty-eight (62%) of 61 with tilted position showed higher position on the right side, and twenty-three (38%) showed higher position on the side. The average transverse dimension(mean SD) was 15.2 ± 0.7mm in men and 14.6 ± 1.0mm in women. The difference of transverse dimension between men and women was statistically significant. CONCLUSION: Tilted position of the adult optic chiasm on coronal MRI was seen in approximately half of normal adults. The average of transverse dimension of normal optic chiasm was 15mm.