In spite of their important impact on populations, a number of diseases--all types of cancer and coronary heart disease in women--are "rare" events for statistical analysis and often analyzed in designs affected by selection and information biases, such as case-control studies. Large cohort studies based on the storage of biological specimens appear to be the most suitable solution for identifying risks for those diseases. Progetto ATENA, a study on the etiology of major chronic diseases in women is based on this design. Ten thousand women, aged 30-69 years, living in the area of the city of Naples, free of cancer and cardiovascular disease, are being recruited over a four-year period. Ten per cent of the cohort is being randomly selected from the electoral roles, the rest will be volunteers. Information on dietary habits, reproductive history, familiarity for chronic disease, active smoking habits and passive smoking exposure, physical activity, and socio-demographic data are being collected. Clinical data such as blood pressure, anthropometry, and electrocardiogram are also taken. All the participants provide biological samples of blood (fasting drawing) and urine (timed morning spot). The biological samples are processed in order to explore the main areas under study (nutritional markers, metabolism, endocrinology, genetics, environmental exposure markers, thrombogenesis). The samples are stored in liquid nitrogen (-196 degrees C) as soon as the blood and urine processing have been finished. An appropriate follow-up information system on the health status of the participants is being set up to estimate incidence and mortality rates.