An agent for preventing or ameliorating vascular endothelial malfunction and arteriosclerosis-related symptoms caused by the progress of vascular endothelial malfunction (e.g., ischemic diseases such as myocardial infarction, angina, and peripheral artery occlusion) or low blood flow-related symptoms (e.g., stiff shoulders, excessive sensitivity to cold, swelling, erectile dysfunction, rough skin and decrease in exercise performance due to skeletal muscle hypoactivity), which has an improved NO production enhancing effect is provided. A NO production enhancer comprising citrulline or a salt thereof and glutathione or a salt thereof as active ingredients. An agent for preventing or ameliorating vascular endothelial malfunction, comprising citrulline or a salt thereof and glutathione or a salt thereof as active ingredients. An agent for preventing or ameliorating a symptom caused by vascular endothelial malfunction, comprising citrulline or a salt thereof and glutathione or a salt thereof as active ingredients.
