Nisin is a heat stable lantibiotic consisting of 34 amino acids. Of these amino acids, there are several unusual amino acids including dehydroalanine, dehydrobutyrine, aminobutyric acid, lanthionine and __ampersandsignbeta;-methyllanthionine. It has antimicrobial activity against many species of Gram positive bacteria, but not Gram negative bacteria due to their outer membrane barriers. However, when used in combination with other chemical or physical treatments that destabilize the outer membranes, nisin can inhibit Gram negative bacteria. Nisin has been used as a food preservative in many food industries because it is legally approved as safe for use in food and beverage. The knowledge on the production and mechanism of antimicrobial action of nisin is important for the understanding how nisin contains unusual amino acids and how it kills sensitive bacteria. The knowledge may also be a factor for the successful application of nisin. Therefore, this review focuses on presenting these two aspects of nisin.