The authors examine the evolution of the PHC approach in historical perspective, present definitions and criteria of what PHC actually means, look upon deviations of conceptual content and practice of PHC and end up with a socio-political as well as a technical critique of the so-called 'selective' PHC. Modern health systems evolved in developing countries modelled on the 'western' biomedical health care systems. Yet even colonial medical services contained also progressive elements, as e.g. the acceptance of the need to de-centralise hospital care to peripheral health posts, or the stress on more rational distribution and utilisation of drugs. The vertical programmes developed under this approach showed clearly their limitations and the conference of Alma-Ata can be looked at as a turning point, where a new model of health care, i.e. PHC, was designed. Though there exists a widespread resistance in industrialised countries against adopting this new model, it was not at all limited only to developing countries. As with every innovative idea, the PHC strategy provoked contradictory views and large differences in interpretation. But, the authors stress, PHC is neither a doctrine, or a theory but the outcome of decades of field-experience of concerned scientists and practitioners. The essential criteria of PHC include: Accessibility: need for improved first contact with the health care system, demanding efforts of decentralising the existing health system without neglecting the quality of care on higher-level medical services. PHC is essentially an action-programme designed around the well-known eight PHC elements, designed to meet effective demand and to rationalise medical offer. The eight elements rather underline the multiplicity of health action required--they are not considered to serve as 'chapters' of PHC policy. PHC is a strategy for re-organising health services. The hospitals should serve the peripheral health centres and not the other way round. At the same time, curative preventive and promotive actions have to be integrated. This necessitates community participation, as the global health problems cannot be solved by the health services alone. PHC in so far re-defines the role of medicine and looks at health in a holistic way. Medicine is being de-mystified and individuals and communities are encouraged to take over responsibility for their own health. This is not at all the consequence of an idealistic view, but derived from field experiences in various circumstances. PHC as a new philosophy of health services delivery therefore, stresses: holistic action for global health issues, equity, participation, and cost/efficiency.(ABSTRACT TRUNCATED AT 400 WORDS)