Increasing problem of resistance to conventional antibiotics has initiated an alarming situation for entire world and hence there exist an immediate need to explore better alternatives for combating resistance. This exploration of substitutes led to discovery of bacteriocins which are considered as natural antimicrobial agents. Bacteriocins are proteinaceous substances ribosomally synthesized from certain bacteria. Bacteriocins producing bacteria include both gram positive and gram negative bacteria. Bacteriocins have been classified in various classes on the basis of amino acids present, producer bacteria, and molecular masses. There are four classes of bacteriocins produced from gram positive bacteria and two classes produced from gram negative bacteria. Bacteriocins exhibit all four mechanisms of microbial inactivation used by conventional antibiotics which are inhibition of cell wall synthesis, disruption of membrane structure and integrity, interference in protein and DNA synthesis. In addition to these conventional drug targets, bacteriocins show novel mechanism of septum formation which results in termination of cell cycle. Bacteriocins have shown a wide range of applications in pharmaceutical industry as an excellent drug for multidrug resistant bacteria as well as against methicillin resistant staphylococcus aureus (MRSA). They have also displayed inhibitory effects against peptic ulcer causing H.pylori and skin infections causing gram positive bacteria. They possess antimicrobial activity not only against bacteria but viruses and fungi are also susceptible to bacteriocins.