Data analyses restricted to areas with health care services provided by the Indian Health Service (IHS) improve the accuracy of American Indian/Alaska Native (AI/AN) cancer statistics. IHS Purchased/Referred Care Delivery Areas (PRCDA) consist of counties which include all or part of an AI/AN reservation and any county or counties which have a common boundary with a reservation. This derived data item facilitates the production of the most accurate and reliable incidence rates for the American Indian/Alaskan Native population and was previously known as IHS Contract Health Service Delivery Area (CHSDA).