<h3>Objective:</h3> To determine whether T2 lesions that go on to become atrophied lesions over time in multiple sclerosis (MS) patients are characterized by differences in their underlying microstructure, as characterized by diffusion tensor imaging (DTI), and its bi-tensor extension. <h3>Background:</h3> Atrophied lesion volume is a recently proposed imaging marker in MS reflecting the shrinkage of lesional tissue into cerebrospinal fluid (CSF). The measure has been shown to be very sensitive to the progression of MS and conversion to a secondary-progressive disease course. A previous study showed that only 13% of the areas that eventually become atrophied lesions over 5-year follow-up, were represented by chronic black holes at baseline. Therefore, the underlying tissue properties of areas that eventually become atrophied lesions remain poorly understood. <h3>Design/Methods:</h3> 141 MS patients underwent 3T MRI at baseline and again after 5.4 years with a protocol that included a 3D T1, FLAIR and diffusion-weighted imaging acquisitions. Atrophied T2 lesion volume was calculated by overlaying baseline T2 lesion masks on follow-up CSF maps. Standard DTI measures, including mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD) were calculated as were free water (FW)-corrected DTI measures along with FW itself. DTI-derived measures were calculated within baseline lesional voxels that went on to become areas of atrophied lesion volume at follow-up. Paired t-tests were compared these values with corresponding tissue that remained lesional. <h3>Results:</h3> WM lesions at baseline that went on to be classified as atrophied LV at follow-up were characterized by significantly worse diffusivity characteristics for all investigated metrics (< .001 for all measures except for FW-corrected AD, p=.012). The largest effect size was seen for FW (d=2.46) followed by conventional RD (d=2.21) and conventional MD (d=2.13). <h3>Conclusions:</h3> Lesions that eventually shrink into CSF are characterized by more extensive microstructural damage compared to those that do not. <b>Disclosure:</b> Dr. Bergsland has nothing to disclose. Dr. Dwyer has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with Serono Novartis and Clare Medical.. Dr. Dwyer has received research support from Michael G. Dwyer received financial support for research activities from Mapi Pharma, Keystone Heart, Protembis and V-WAVE Medical.. Dr. Jakimovski has nothing to disclose. Dr. Weinstock-Guttman has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with Biogen, , Novartis, Genentech, EMD Serono, Abbvie, Mallickrodt, Bristol Myers.. Dr. Weinstock-Guttman has received research support from Biogen, Novartis, Genentech, and EMD Serono..Dr. Zivadinov has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with Received personal compensation from EMD Serono, Genzyme-Sanofi, Celgene, and Novartis. Dr. Zivadinov has received research support from Received financial support for research activities from Genzyme-Sanofi, Novartis, Celgene, KeyStone Heart, V-WAVE Medical, Mapi Pharma and Protembis.