Histamine is synthesized from L-histidine by histidine decarboxylase and is involved in a variety of physiologic responses, such as inflammation, type I allergy, gastric acid secretion and neurotransmission. In the arteriosclerotic lesions, histamine produced by macrophage-derived foam cells acts on smooth muscle cells, endocrine cells and inflammation cells through the specific histamine receptors and regulates the expression of many molecules concerned with inflammatory reaction. A regulatory system of chronic inflammatory reaction by the histamine network is involved in the formation and development of arteriosclerosis.