OBJECTIVE: To explore the likely impact of future trajectories of morbidity and mortality in Australia. METHODS: Estimates of mortality and morbidity were obtained from a previous assessment of Australia's health from 1993 to 2003, including projections to 2023. Outcomes of interest were the difference between life expectancy (LE0) and health-adjusted life expectancy (i.e. absolute lost health expectancy (ALHE0)), ALHE0 as a proportion of LE0 and the partitioning of changes in ALHE0 into additive contributions from changes in age- and cause-specific mortality and morbidity. RESULTS: Actual and projected trajectories of mortality and morbidity resulted in an expansion of ALHE0 of 1.22 years between 1993 and 2023, which was equivalent to a relative expansion of 0.7% in morbidity over the life course. Most (93.8%) of this expansion was accounted for by cardiovascular disease, diabetes and cancer; of these, the only unfavourable trend of any note was increasing morbidity from diabetes. CONCLUSIONS: Time spent with morbidity will most likely increase in terms of numbers of years lived and as a proportion of the average life span. This conclusion is based on the expectation that gains in LE0 will continue to exceed gains in ALHE0, and has important implications for public policy. WHAT IS KNOWN ABOUT THE TOPIC? Although the aging of Australia's population as a result of declining birth and death rates is well understood, its relationship with levels of morbidity is not always fully appreciated. This is most noticeable in the policy discourse on primary prevention, in which such activities are sometimes portrayed as having unrealised potential with respect to alleviating growth in health service demand. WHAT DOES THIS PAPER ADD? This paper sheds new light on these relationships by exploring the likely impact of future trajectories of both morbidity and mortality within an additive partitioning framework. The results suggest a modest expansion of morbidity over the life course, most of which is accounted for by only three causes. In two of these (cardiovascular disease and cancer), the underlying trends in both mortality and morbidity have been favourable for some time due, at least in part, to success in primary prevention. WHAT ARE THE IMPLICATIONS FOR PRACTITIONERS? Although there may be good arguments in favour of a greater focus on primary prevention as currently practiced, reducing overall demand for health services is unlikely to be one of them. To make such an argument valid, policy makers should consider shifting their attention to the effectiveness of primary prevention as it relates to causes other than cardiovascular disease and cancer, particularly those with a predominantly non-fatal impact, such as diabetes and degenerative diseases of old age.