INTRODUCTION: The uncinate fasciculus (UF) consists of core fibers connecting the frontal and temporal lobes and is considered to be related to cognitive/behavioral function. Using diffusion tensor tractography, we quantitatively evaluated changes in fractional anisotropy (FA) and the apparent diffusion coefficient (ADC) of the UF by tract-specific analysis to evaluate the damage of the UF in patients with amyotrophic lateral sclerosis (ALS). METHODS: We obtained diffusion tensor images of 15 patients with ALS and 9 age-matched volunteers. RESULTS: Patients with ALS showed significantly lower mean FA (P = 0.029) compared with controls. No significant difference was seen in mean ADC. CONCLUSION: The results suggest that damage of the UF in patients with ALS can be quantitatively evaluated with FA.