The complete genome sequence of Enterococcus faecalisV583, a vancomycin-resistant clinical isolate, revealed that more than a quarter of the genome consists of probable mobile or foreign DNA. One of the predicted mobile elements is a previously unknownvanB vancomycin-resistance conjugative transposon. Three plasmids were identified, including two pheromone-sensing conjugative plasmids, one encoding a previously undescribed pheromone inhibitor. The apparent propensity for the incorporation of mobile elements probably contributed to the rapid acquisition and dissemination of drug resistance in the enterococci.