PERSPECTIVES
This section will publish short contributions from readers containing a view, a hypothesis or a point for discussion on an issue of public health interest. Contributions (850 words, no references) are welcome. The following contribution is of unusual length and format, to inaugurate the section. Julio Frenk explains its importance.
Julio Frenk
Executive Director, Evidence and Information for Policy, WHO
Avedis Donabedian is the most influential thinker on the quality of health care. Through a corpus of articles, books and lectures spanning more than three decades, he has laid the foundations for a deeper understanding of this important area of health systems. His seminal paper of 1966 (1) introduced the concepts of structure, process and outcomes, which remain to our day as the dominant paradigm for the evaluation of the quality of health care. An indicator of the importance of this paper is the fact that it is one of the very few "Citation classics" in the field of health systems research (2). A culminating point in this remarkable body of work is Donabedian's series of three volumes on Explorations in quality assessment and monitoring, which are the definitive systematization of concepts, methods and evidence (3).
To add to the eight books and over 50 peer-reviewed articles by Donabedian, one of his very few unpublished pieces has recently surfaced. It is the text of a lecture that he delivered in 1976 and, like so much of what Donabedian has written, is a visionary contribution, far ahead of its time. Today, when countries at all levels of development and with all types of political system are actively rethinking their health systems, assessing performance has become an imperative. Provider competence is a crucial component of such assessment.
With the kind permission of the author, we offer to the readers of the Bulletin this unique article as part of the special theme on health systems. It gives us a glimpse into a topic of capital importance and into the creative mind of one of the true giants of this field. 
1 Donabedian A. Evaluating the quality of medical care. Milbank Memorial Fund Quarterly, 1966, 44: 166206.
2 This week's citation classic. Current Contents: Social and Behavioral Sciences, 1983, 15(6): 18.
3 Donabedian A. Explorations in quality assessment and monitoring. Vol I. The definition of quality and approaches to its assessment, 1980; Vol II. The criteria and standards of quality, 1982; Vol III. The methods and findings of quality assessment and monitoring: an illustrated analysis. Ann Arbor, Health Administration Press, 1985.