In this paper the concepts, objectives, design, and data analysis procedures of the EuroNatal study are described. This study started in 1996 and is a concerted action including 14 countries in Europe. The EuroNatal study aims at determining the validity of national perinatal mortality rates as an outcome indicator for the quality of antenatal and perinatal care. It is based on a conceptual model describing the relationships between differences in quality of antenatal and perinatal care, maternal and infant risk factors, variation in applied definitions, reliability of registration procedures and practices, and the outcome in terms of "true" and "observed" differences in perinatal mortality. In the first part of the study data is collected at national and aggregate level; in the second part data is collected retrospectively on individual cases of perinatal mortality in a regional sample area. Analysis of the individual cases of perinatal mortality will be by means of a perinatal audit conducted by an international expert panel. The project builds upon the work done by the participants in their respective countries. By applying common research protocols, international comparability of data collection will be enhanced and will help to create a common body of knowledge in the area of perinatal epidemiology and perinatal care. Comparison between countries is likely to lead to new insights into the strengths and weaknesses of antenatal and perinatal care systems of individual countries.