It is important to consider all aspects of the burden of a disease using a range of outcome measures - not only morbidity and mortality - but also the effect on patient lifestyle and healthcare resources, and the economic impact on the patient, healthcare system and society. Only with this complete appraisal can the full extent of the disease burden be assessed. It is also useful to look to the future to see how the number of patients affected by the disease is likely to change--this information is useful to place in context the consequences of any proposed interventions. The burden of asthma and chronic obstructive pulmonary disease (COPD) is considerable. The main cost element of asthma is medication, whereas hospitalisation accounts for the largest proportion of costs for COPD. Consequently, in The Netherlands, the annual cost per patient of managing COPD is almost 3 times as high as that of asthma. Together, the two respiratory conditions cost the Dutch healthcare system $US346 million for direct medical costs in 1993, amounting to 1.3% of the total healthcare budget. The burden of COPD is expected to increase considerably in the future, reflecting the previous smoking habits of an aging population. Even if the current decline in the prevalence of smoking continues, by 2015 there will be a 76% increase in the prevalence of COPD (with the increase higher among women than men), compared with the prevalence in 1994. This is largely due to the aging of the population. This will need to be considered by decision-makers allocating funds to healthcare services. It also further underlines the need to maximise the value gained from limited resources available to manage asthma and COPD.