We have recently shown that heart failure admission rates continue to increase in the UK -- particularly in older age groups. As hospital activity represents the major cost component of health care expenditure related to heart failure, this study evaluated the current cost of this syndrome to the National Health Service (NHS) in the UK. We applied contemporary estimates of health care activity associated with heart failure to the whole UK population on an age and sex-specific basis to calculate its cost to the NHS for the year 1995. Direct components of health care included in these estimates were hospital admissions associated with a principal diagnosis of heart failure, associated outpatient consultations, general practice consultations and prescribed drug therapy. We also calculated the cost of nursing-home care following a primary heart failure admission and the cost of hospitalisations associated with a secondary diagnosis of heart failure. Adjusting for probable increases in hospital activity and the progressive ageing of the UK population, we have also projected the cost of heart failure to the NHS for the year 2000. We estimated that there were 988000 individuals requiring treatment for heart failure in the UK during 1995. The 'direct' cost of health care for these patients was estimated to be pound 716 million, or 1.83% of total NHS expenditure. Hospitalisations and drug prescriptions accounted for 69 and 18% of this expenditure, respectively. The additional costs associated with long-term nursing home care and secondary heart failure admissions accounted for a further pound 751 million (2.0% of total NHS expenditure). By the year 2000, we estimated that the combined total direct cost of heart failure would have risen to pound 905 million -- equivalent to 1.91% of total NHS expenditure. Using well-validated sets of data, these findings re-confirm the importance of heart failure as a major public health problem in the UK. The annual direct cost of heart failure to the NHS in 2000 is likely to be of the order of 1.9% of total expenditure -- the predominant cost component being hospitalisation.