PURPOSE: MR is the most useful imaging method in evaluating the anatomic changes of the optic chiasm (OC). The purpose of this study is to investigate the relationship between the OC displacement and visual manifestations. MATERIALS AND METHODS: We retrospectively reviewed 44 patients who showed displacement of OC on brain MR. The pattern of OC displacement was classified into 3 groups according to following criteria: group A included the patients with OC displacement only due to empty sella;group B represented the patients with OC displacement by a lesion and the border between the lesion and OC was distinct;and group C was the patients with OC displacement by a lesion and had a indistinct border or thinning of the OC. RESULTS: Visual symptoms and signs were noted in 12 patients and the most common sign was bitemporal hemianopsia. In group A(7 patients), the visual symptoms and signs were seen in only one patient(14%), in whom contracted visual fields persisted since previous pituitary apoplexy had developed. In group B(30 patients), the visual symptoms and signs were seen in 4 patients(13%) who had tumorous conditions except one case of cysticercosis. In group C(7 patients), the visual symptoms and signs were seen in all patients (100%). CONCLUSION: The more OC is compressed, the more the prevalence of visual symptoms and signs increases. However, there was no correlation between the occurrence of visual symptoms and the presence of OC displacement only without compression.