OBJECTIVE: To determine the effects of soy consumption on markers of inflammation and endothelial function in postmenopausal women with the metabolic syndrome. RESEARCH DESIGN AND METHODS: This randomized cross-over clinical trial included 42 postmenopausal women with the metabolic syndrome. Participants were randomly assigned to consume a control diet (Dietary Approaches to Stop Hypertension [DASH]), soy protein diet, or soy nut diet, each for 8 weeks. Red meat in the DASH diet (one serving/day) was replaced by soy protein in the soy protein diet and by soy nut in the soy nut diet. RESULTS: For nitric oxide levels, the difference from the control diet was 9.8% (P < 0.01) on the soy nut and -1.7% (P = 0.10) on the soy protein diets. The difference from the control diet for serum E-selectin was -11.4% (P < 0.01) on the soy nut consumption and -4.7% (P = 0.19) on the soy protein diet. Soy nut consumption reduced interleukin-18 compared with the control diet (difference from the control diet: -9.2%, P < 0.01), but soy protein did not (difference from the control diet: -4.6%, P = 0.14). For C-reactive protein, the difference from the control diet was -8.9% (P < 0.01) on the soy nut diet and -1.6% (P < 0.01) on the soy protein diet. CONCLUSIONS: Short-term soy nut consumption reduced some markers of inflammation and increased plasma nitric oxide levels in postmenopausal women with the metabolic syndrome.