Increased emphasis is being placed on improving outcomes for abused and neglected children served by the child welfare system. To achieve this goal, the notion of "best practice" is widely embraced. Unfortunately, there is no consensus on its definition. Various interpretations include (a) practice wisdom, (b) emulating other systems, (c) expert consultants, (d) professional guidelines, and (e) evidence-based practice. In this article, the authors describe the advantages and disadvantages of each of these definitions. While all of them have a role to play in improving results of child welfare interventions, the authors argue that best practice is optimally defined as evidence-based practice. At the same time, there are many difficulties in employing this form of best practice, including a lack of evidence, the transfer of information, and the organizational culture in which the worker operates. Suggested solutions to these difficulties are discussed.