The aim of this study was to assess the relationship between body fat mass (BFM) and erectile dysfunction (ED) in Korean men. This study was a cross-sectional study using data on 208 men (the mean age=67.4+/-8.2). ED was diagnosed by the International Index of Erectile Function (IIEF)-5 and body fat percentage (BF%) was quantified with bioelectrical impedance. BF% was divided into quintiles (quintile 1: < or =20.5%, quintile 2: 20.6-23.2%, quintile 3: 23.3-25.8%, quintile 4: 25.9-28.8%, quintile 5: > or =28.9%). Using subjects with quintile 3 of BF% as reference, the adjusted odds ratios of subjects with the lowest quintile of BF% and with the highest quintile were 9.29 (95% CI: 2.29-37.72) and 4.99 (95% CI: 1.37-18.09), respectively. This study showed that BFM and ED had a U-shaped relationship in Korean men. These findings suggest that not only obesity but also a low BFM may be a risk factor of ED in Asians.