BACKGROUND: The Regional Register of Cardiovascular Diseases of the Regional Health Authority of Western Norway was established to enable epidemiologic research on a national level before the recent advent of the Norwegian health register with personal identification. Hospital admission rates, and case-fatality were compared with regional mortality rates for cardiovascular diseases. MATERIAL AND METHODS: The register contains data on 231,857 patients with cardiovascular diseases or diabetes mellitus admitted to hospitals in Western Norway (Rogaland, Hordaland and Sogn og Fjordane) 1972-2002. The hospital data were supplemented with data from the national cause of death register (national identification number was used to link up the information). RESULTS: The admission rates for cardiovascular diseases increased moderately in Western Norway from 1992 through 2001. At the same time a marked reduction was seen in mortality rates for these diseases. For acute myocardial infarction, the admission rates decreased slightly from 1992 through 2000, and then increased in 2001. Case-fatality from acute infarction was substantially reduced throughout the decade, most notably for those aged 65 years or more. Among those who died of acute infarction the first 24 hours, the fraction who died outside of hospital was high (78.3%). INTERPRETATION: Hospital admission rates for cardiovascular diseases do not parallel the simultaneous decrease in mortality rates. The Regional Register of Cardiovascular Diseases demonstrates the possibilities for etiological research and the limitation of mortality statistics alone.