Credentialing in nursing has grown increasingly complicated. Nurses frequently exhibit confusion about terminology, process, and required versus voluntary programs. This article reviews credentialing in health care from both a practical and an historical perspective. Components of credentialing are defined and their application in nursing is briefly discussed. Categories of certification are clarified. Professional certification programs currently available for pediatric and maternal-child health nurses are summarized in detail. Rationale for the increasing popularity of the certification credential are explored.