This article is first in a series of reports describing an evidence-based approach for evaluating information associated with periodontal treatment. Two main differences distinguish this approach from the traditional one, which is based largely on clinical experience. The evidence-based approach requires that investigators emphasize the importance unibiased data (evidence) and use specific rules of evidence to quantigy their recommendations. Search, evaluate, and rank are the three steps used for gathering information from the literature. The information (evidence) can then be used to formulate new decision pathways, practice guidelined, and treatment recommendations.