Staphylococcal isolates commonly contain one or more plasmids. The role of plasmids as mediators of bacterial adaptation has been clearly illustrated by the rapid emergence of antibiotic resistance in many bacterial genera, including staphylococci. Analyses of prototypical plasmids from Staphylococcus aureus have revealed they carry multiple systems that facilitate their efficient inheritance and transmission, which promote plasmid carriage independently of any selectable advantage they may confer on their host. Current understanding of the molecular mechanisms of these plasmid housekeeping systems will be described.