Recent research, concentrating on the significance of L-arginine, a basic amino acid, with respect to medical biochemistry is noteworthy. The fact that L-arginin is a nitrogen donor in nitric oxide (NO) biosynthesis provokes interest toward this amino acid. In healthy adults arginine is not classified among essential amino acids, while in children and adoloscents it is essential. In serious states of disease, especially in cases of sepsis where it's positive effects are noted, arginine may be considered as‘ conditionally essential'. It is synthesized from the breakdown of citrulline, glutamate, proteins and catabolised to ornithine and urea. Arginine participates in varıous biosynthesis such as protein, glucose, NO, ornithine, urea, creatine agmatine and polyamine synthesis as well as existing in the structure of ADH and tuftsin. The supplementatıon of L arginine has positive effects primarily on the cardiovascular system and systems such as the immune, urogenital, endocrine and locomotor systems. L-arginine supplementation seems to be a hopeful treatment strategy in cardiovascular disease, pulmonary hypertension, male infertility, as well as in the accelerated healing of wounds and burns and septicemia.