Research into bacteriophage and bacteriophage resistance in the lactic acid bacteria has moved into a new and exciting dimension in recent years. Mechanisms such as adsorption inhibition, restriction and modification, and abortive infection which have been described phenotypically over the past decade are now being subjected to molecular analysis, and this has led to a better understanding of the nature and variety of resistance systems employed by lactic acid bacteria to combat phage attack. in addition, analysis of different bacteriophage has increased our knowledge of these ubiquitous particles to the point where it is possible to construct novel phage resistances based on the phage genome. This review will briefly outline the recent progress in the molecular analysis of bacteriophage-host interactions, bacteriophage resistance and counter resistance, and the construction of novel resistance mechanisms. In particular, recent evidence regarding the mechanisms of resistance employed by the conjugative plasmid pNP40 will be described in some detail. In addition, an instance will be described in which pNP40 has been used in the construction of phage resistant starters which have been successfully exploited by the dairy industry.