The review and verification of credentials and the granting of clinical privileges are required of every hospital to ensure that members of the medical staff are competent and qualified to provide specified levels of patient care. The credentialing process involves the following: (1) assessment of the professional and personal background of each practitioner seeking privileges; (2) assignment of privileges appropriate for the clinician's training and experience; (3) ongoing monitoring of the professional activities of each staff member; and (4) periodic reappointment to the medical staff on the basis of objectively measured performance. We examine the essential elements of a credentials review for initial and renewed medical staff appointments along with suggested criteria for the delineation of clinical privileges. Sample forms for the delineation of privileges can be found on the American Academy of Pediatrics Committee on Hospital Care Web site (http://www.aap.org/visit/cmte19.htm). Because of differences among individual hospitals, no 1 method for credentialing is universally applicable. The medical staff of each hospital must, therefore, establish its own process based on the general principles reviewed in this report. The issues of medical staff membership and credentialing have become very complex, and institutions and medical staffs are vulnerable to legal action. Consequently, it is advisable for hospitals and medical staffs to obtain expert legal advice when medical staff bylaws are constructed or revised.