The complete sequence of pMRC01, a large conjugative plasmid from Lactococcus lactis ssp, lactis DPC3147, has been determined, Using a shotgun sequencing approach, the 60 232 bp plasmid sequence was obtained by the assembly of 1056 underlying sequences (sevenfold average redundancy), Sixty-four open reading frames (ORFs) were identified, Analysis of the gene organization of pMRC01 suggests that the plasmid can be divided into three functional domains, with each approximately 20 kb region separated by insertion sequence (IS) elements. The three regions are (i) the conjugative transfer region, including a 16-gene Tra (transfer) operon; (ii) the bacteriocin production region, including an operon responsible for the synthesis of the novel bacteriocin lacticin 3147; and (iii) the phage resistance and plasmid replication region of the plasmid, The complete sequence of pMRC01 provides important information about these industrially relevant phenotypes and gives insight into the structure, function and evolution of large Grampositive conjugative plasmids in general. The completely sequenced pMRCO1 plasmid should also provide a useful framework for the design of novel plasmids to be incorporated into starter strain improvement programmes for the dairy industry.