Some groups cover several hospitals in which case the anesthesiologist may be posted to different hospitals depending on the need. Some independent anesthesiologists in locations where exclusive contracting with hospitals is rare, may work at different hospitals- they tend to work with a small number of surgeons and will travel with those surgeons from hospital to hospital. Rarely, physicians may engage in part time employment with two different groups at two different hospitals. This must be done with rigid scheduling and may make vacations difficult.