OBJECTIVES: Identify combinations of cancer, cerebrovascular, diabetes, respiratory, CNS, and infectious concomitant illnesses in cardiovascular disease causing increasing risks of dying at ages under 65 and assess subsequent changes in the prevalence of these combinations. METHODS: Combinations of multivariate linear regressions and standard SAS codes were applied to data drawn from the 1991-1996 Multiple Causes of Death Files. The 5-year numbers of deaths, cardiovascular-associated, and hypertension-associated deaths were 11,056,565, and 5,486,234 (<65=2,769,731), and 904,770 (<65=166,007), respectively. RESULTS: During 1991-1996, mortality rates in individuals with CV disease decreased: in <65 - 6% and >=65 - 3%. The prevalence of cardiovascular-associated deaths has decreased from 39.6% to 39.2% of all deaths <65. The following combinations of comorbidities in individuals <65 with cardiovascular morbidity demonstrated increasing prevalence (PR), mortality rates (MR) and relative MR of <65/>=65: diabetes (PR -12%, MR - 6%, RMR - 1.7%); CNS (PR -13%, MR - 8%, RMR - -6%); infectious (PR -3%, MR - -1%, RMR - -3%). In addition, diabetes in combination with cerebrovascular, cancers and respiratory comorbidities caused increased, up to 36%, risk of dying at ages under 65. A 69% (in CV+diabetes) growth of the ischaemic heart disease case-fatality was the highest increase in case-fatality across all primary causes of death. In <65, mortality rates of hypertension and with diabetes grew 14% and 26% ('25-29' - 66%), respectively. Among 55 primary causes of death in hypertension, the highest increase in case-fatality occurred for cns diseases (dementia, psychoses, Alzheimer's, paralysis), diabetes with renal manifestations (115%), hypertensive heart (95%), and respiratory diseases (COPD, pneumonia, asthma, emphysema). CONCLUSION: Although cardiovascular mortality has decreased overall, disease management for patients with cns, diabetes, and infectious comorbidities calls for further research because these groups of patients exhibit increasing risks of dying at the ages under 65. Related premature mortality costs and productivity losses will be presented.