Soy protein intake has been postulated to improve lipid profiles, glucose homeostasis, and blood pressure. However, data linking soy protein intake and metabolic syndrome (MetS) are limited. We evaluated the association between soy protein intake and the risk of MetS and its components among middle-aged and elderly Chinese. A cross-sectional study was conducted among 2811 Chinese men and women aged 50-70 y, who were free of diagnosed cardiovascular diseases and cancers. Dietary data, including soy protein intake, was collected using a 74-item FFQ. MetS was defined using the updated National Cholesterol Education Program Adult Treatment Panel III criteria for Asian-Americans. We used multivariate logistical regression models to quantify these associations. The median level of soy protein intake was 7.82 g/d (7.64 g/d in men and 8.02 g/d in women). Overall, the association of soy protein intake and the risk of MetS differed between men and women (P for interaction = 0.008). In men, the adjusted odds ratio comparing the extreme quartiles was 1.64 (95% CI: 0.95-2.81; P-trend = 0.077), whereas for women, it was 0.66 (95% CI: 0.42-1.03; P-trend = 0.138). Soy protein intake was positively associated with hyperglycemia (P-trend = 0.005) in men, whereas it was inversely associated with elevated blood pressure (P-trend = 0.049). It was not associated with any component in women. In conclusion, habitual soy protein intake may have sex-dependent effects on risk of MetS in middle-aged and elderly Chinese. © 2008 American Society for Nutrition.