The physician is ultimately responsible, and potentially liable, for any care or other service provided to his or her patients by office staff. In short, office staff members' malpractice is the physician's malpractice. Note that Illinois law requires that advanced practice nurses and physician assistants, respectively, establish written collaborative agreements and written practice guidelines with the physician(s) who supervise them. For further information on practice acts and rules governing the supervision of nurses, advanced practice nurses, and physician assistants, visit the Illinois Department of Professional Regulation's website at http://www.dpr.state.il.us.