Arginase (L-arginine ureohydrolase) is present in mammals and plants. In humans, arginase is expressed predominantly in the liver, and to lesser degrees in breast, kidney, testes, salivary glands, epidermis and erythrocytes. Arginase catalyzes the conversion of arginine to ornithine and urea, important for protection against NH3 toxicity and for cell growth and repair. Excessive arginase activity has been linked to cardiovascular diseases, also contribute to vascular structural problems and neural toxicity. Studies show that arginase inhibitors have been proven to be beneficial in cardiovascular and nervous system diseases. Simple, direct and automation-ready procedures for measuring arginase inhibition are highly desirable in Research and Drug Discovery.