To establish a framework for the Intensive Care Units (ICU) Register in Croatia, and examine the relation between their present organization and medical practices and their outcome performances.The survey of a total of 123 ICUs in Croatia was conducted between February 1 and October 31, 2001. Census questionnaires were filled out by ICU chiefs of staff. Demographic data, data on hospital and ICU structure and organization, disposable equipment, admission and discharge decision-making, outcome, and patient demographic data were collected for February 1, 2001. Descriptive statistics was used for data analysis.On February 1, 2001, there were 123 ICUs in Croatia. The questionnaire was filled out by 117 ICU chiefs of staff (95% response rate). The total number of ICUs beds was 900, comprising 3.3% of all hospital beds. Croatian ICUs were divided into 13 subtypes; 89% of them were adjoined to hospital departments of various subspecialties and only 13 (11%) were freestanding. The number of ICUs per hospital, number of ICU beds, quantity of disposable equipment, and number of permanently employed medical and nursing staff within hospitals and individual units increased as hospitals enlarged. Also, the number of mixed surgical/medical and coronary care/medical units decreased, and specialized units became prevalent. The mortality data in Croatian ICUs were similar to those reported elsewhere in the world: the lowest mortality was found in psychiatric ICUs (3%) and the highest in an ICU for infective diseases (30%), followed by neurological (19%), medical (17%), and respiratory (16%) ICUs.Establishing a database on intensive care medicine and assessing the performance of ICUs in Croatia could serve as a model for improvement of ICU service in other transition countries.