Although Intensive Care Units (ICU) are present in most of the Italian Hospitals for acute patients, the heterogeneity of the patients case-mix and the large variation in structural, organizational and staffing arrangements have limited the feasibility and precision of evaluation studies aimed at assessing the quality of health care delivered and its impact on patients outcomes. To our knowledge there has been no nationwide study aimed at assessing the quality and effectiveness of the delivered care in samples of ICUs and patients that are representative of the source populations. To study the effects of variations in health care practices on the outcome of the patients admitted in ICU, we designed a multicentric observational study involving 120 ICUs within the country. The present study is the first part of a project involving a network of Intensive Care Units gathered under the name of GiViTI-Italian Group for the Evaluation of the Interventions in Intensive Care-that is representative of the national Italian reality in the field. The idea of a large collaborative group acting in the field of Intensive Care stands in line with several quality, effectiveness and resource utilization studies that are ongoing in other European countries and is also the result of a series of smaller-scale experiences carried out by other Italian groups eventually emboied in the GiViTI project. In the framework of the ongoing long term, multisite, and multidisciplinary project, the present study calls for the recruitment of all consecutive patients seen at the participant centers during a two months period.(ABSTRACT TRUNCATED AT 250 WORDS)