As the projected survival time of human immunodeficiency virus (HIV) and hepatitis C (HCV) increase, long-term systemic effects of these diseases and their treatments remain an active area of research¹. Particularly in the HIV population, which is predisposed to infection, imaging can play an important role in monitoring these effects. Racial differences in visceral fat and hepatic fat fraction (FF) are known^2,3, however a need exists to determine if these differences vary in patients with common chronic diseases. The purpose of this work is to compare differences in visceral fat volume and hepatic FF between African American (AA) and Caucasian (CA) men with HIV, HCV, or co-infection (HIV/HCV) against an age-matched control population. We measured visceral fat at three vertebral disc levels (L23, L34, L45) with 3T MRI [3-slice average fat volume (cc) from axial IDEAL, FOV=50x50 cm, 10 mm slices, NEX=0.5], and calculated fat volume using a semi-automatic contour-based segmentation by a single observer. We measured hepatic FF by MRS, FF = Fat / (Fat + Water), using single-voxel PRESS [TR/TE=2500/30 ms, 20x20x20 mm, water suppressed (NEX=64), unsuppressed (NEX=8)]. We compared differences in fat deposition in the viscera and liver between AA and CA men with HIV, HCV, and HIV/HCV, and in an age-matched control population, and included a homeostatic model assessment of insulin resistance (HOMA-IR) measurement to control for insulin resistance². The breakdown of the 197 men studied was: Control-AA (n=38, mean age=53.0 ± 6.1); Control-CA (n=33, mean age=51.2 ± 8.9); HIV-AA (n=13, mean age=55.6 ± 9.0); HIV-CA (n=47, mean age=53.6 ± 8.2); HCV-AA (n=18, mean age=58.6 ± 3.1); HCV-CA (n=28, mean age=57.2 ± 5.4); HIV/HCV-AA (n=8, mean age=56.5 ± 6.1); HIV/HCV-CA (n=12, mean age=52.9 ± 5.7). Results were analyzed using a Wilcoxon Signed-Rank Test due to non-uniform distribution.There were no adverse events reported during this study. Results by Wilcoxon Signed-Rank Test are summarized in Table 1. In controls, AA men showed a non-significant trend of less visceral fat (p<0.166), and less hepatic FF (p<0.204) than CA men. In HIV, AA men showed significantly less visceral fat (p<0.028) and significantly less hepatic FF (p<0.024) than CA men. In HCV, we see no observable difference in visceral fat (p<0.827) or hepatic FF (p<0.511) by race. In HIV/HCV, we also see no observable difference in visceral fat (p<0.873), or hepatic FF (p<0.323) by race. There was no significant difference in insulin resistance measured by HOMA-IR between any groups analyzed. MR measurement of visceral fat volume by IDEAL imaging and of hepatic FF by single-voxel MRS show racial differences in fat storage vary significantly in common chronic diseases. As the prevalence of metabolic syndrome increases⁴, this co-morbidity can affect physician decisions on medication. Ability to judge abnormal fat deposition and the presence of metabolic syndrome is dependent on knowledge of the population, which this work shows is dependent on not only disease state but also ethnic group. Future work should examine the differences between the populations presented, as well as differences based on treatment history for chronic liver conditions, although these studies require a larger population. In this study, we observed AA men to have a trend towards less MR-measured visceral fat and hepatic FF than CA men in a control population. This difference was enhanced and was significant in the HIV population, while there was no observable difference in the HCV or HIV/HCV populations, indicating a need to consider both race and disease status prior to interpretation of visceral or hepatic FF findings.