BACKGROUNDLogistic, cultural, educational, and other barriers can impede the delivery of high‐quality cancer care to underserved patients. Patient navigation services represent one innovation for addressing perceived barriers to care encountered by disadvantaged patients. In this report, the authors have 1) defined patient navigation, distinguishing it from other cancer support services; 2) described how programs are organized; and 3) discussed the need for research on program effectiveness.METHODSInformation was examined on navigation programs published in the scientific literature and on line. Qualitative research also was conducted, consisting of direct observation of patient care in cancer clinics with and without navigators in northern California, in‐person interviews with personnel and patients in the clinics observed, and telephone interviews with navigators at four sites across the United States.RESULTSThe authors found that navigation services have been implemented at all stages of cancer care: prevention, screening, treatment, and survival. Navigators differ from other cancer support personnel in their orientation toward flexible problem solving to overcome perceived barriers to care rather than the provision of a predefined set of services. There are no rigorous demonstrations of the effects and effectiveness of navigation, although such studies are underway.CONCLUSIONSCurrently, patient navigation is understudied, and literature documenting its effects and effectiveness is scant. Rigorous studies are needed of the navigator role and program costs and benefits. Such studies will facilitate an assessment of program effectiveness, feasibility across a range of health care settings, and performance relative to alternative approaches for addressing barriers to care among the underserved. Cancer 2005. © 2005 American Cancer Society.