Background: While much of structural imaging has focused on gray matter, the quantification of white matter integrity is of interest not only because of the noted white matter pathology seen in Alzheimer’s disease (AD), but also because of the apparent breakdown of myelin in AD. To date there has been no longitudinal study of white matter integrity within asymptomatic samples at elevated risk for late-onset AD, the purpose of this study. Methods: Cognitively normal participants age 50 years and above were chosen from an ongoing longitudinal study, comparing those with increased genetic risk for AD to matched controls. 95 of the high-risk and 91 of the controls had structural scans at baseline (Time 1) and 87 high-risk and 74 controls at three-year follow-up (Time 2). Participants were imaged at each time point on the same 1.5 Tesla Philips Intera-NT system equipped with Galaxy gradients (66mT/m at 110 mT/m/s). High resolution anatomical images of the brain for structural measurements were acquired using a T1weighted, 3D MP-RAGE (Magnetization Prepared Rapid Acquisition Gradient Echo) sequence with the following parameters: TR 8.6 ms, TE 3.9 ms, FOV 240 mm, 8, matrix size 256x256, slice thickness 1.5 mm, 124 slices). Pre-processing was performed using a semiautomated method, followed by the manual removal of remaining skull and dura. All measurements were conducted by one rater blind to group status. Scans were then segmented into separate tissue classes using an adaptive fuzzy C-means algorithm. Volumes of gray matter and white matter tissue as well as total brain volume were calculated. Results: At both Time 1 and Time 2, the high-risk sample showed significantly smaller white matter volumes (Time 1 p 0.05, Time 2 p 0.04). Change across the time points, however, did not significantly differ between groups (control -50ccm, high-risk -53.28ccm). Conclusions: While the similar rate of white matter loss across groups may reflect aging, this would not provide an explanation for the initial significantly smaller white matter volume seen in the high-risk group. Further study is needed to more fully understand the significance of reduced white matter volume as it relates to AD. P1-317 DIFFUSION TENSOR IMAGING IN FRONTOTEMPORAL LOBAR DEGENERATION