Aim. 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.
Conclusion. 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.