Zinc complex of L-carnosine (L-CAZ; generic name Polaprezinc) is the first drug for oral administration in which zinc plays an essential role. L-CAZ was approved as an anti-ulcer drug of membrane protection type. Characterization of L-CAZ was achieved by various spectroscopic methods along with elemental analysis. Zinc ion coordinates with L-carnosine to form a quadridentate 1:1 complex of polymeric nature in order to maintain low strain of chelate rings. L-CAZ can remain in stomach juice without rapid dissociation and adhere to ulcerous lesion specifically, after which L-carnosine and zinc are released to heal the ulcer. L-CAZ exhibited high efficacy in clinical use without any serious side effect. L-CAZ exhibited an inhibitory effect on Helicobacter pylori. Physicochemical aspects on carnosine, zinc, and zinc complex can explain favorable features of L-CAZ as a drug.