Aims: To outline the key concepts and principles of the Delphi technique.
Methods: Reference is made to a selection of studies that illustrate a variety of methodological interpretations. Drawing on Heshusius's concept of 'goodness criteria', particular emphasis is given to the question of scientific merit and means of evaluation.
Conclusions: Although the technique should be used with caution, it appears to be an established method of harnessing the opinions of an often diverse group of experts on practice-related problems.