BACKGROUND AND OBJECTIVE Selection of antiretroviral therapy (ART) for antiretroviral-experienced patients should involve balancing multiple factors, including clinical efficacy, adverse-event risk, resistance concerns, cost effectiveness and expected budget impact. The efficacy of a regimen and its durability, as demonstrated in controlled clinical trials, must be considered in the light of short- and long-term economic impacts on the healthcare system. These impacts may vary based on drug costs, costs of reported adverse effects, the regimen's likelihood of contributing to viral resistance to second-line therapies and the marginal cost differences between other healthcare resources used over a patient's lifetime. Risk of coronary heart disease (CHD) may be of concern in the selection of ART, because differences in CHD risk factors have been reported for different regimens, and heart disease is both a deadly and costly condition. This study set out to estimate the long-term combined effects of HIV disease and antiretroviral-related risk for CHD on quality-adjusted survival and healthcare costs for antiretroviral-experienced patients in the UK, Spain, Italy and France. METHODS A previously validated Markov model was updated with 2006 cost estimates for each of the four countries and supplemented with the Framingham CHD risk equation. In the model, the average patient was male, aged 37 years, with a baseline 10-year CHD risk of 4.6%. Patients started with either lopinavir/ritonavir (LPV/r) or ritonavir-boosted atazanavir (ATV+RTV) as the protease inhibitor (PI). Clinical trial results, local drug costs and AIDS and CHD cost estimates were used to estimate the differences between these two therapies. RESULTS There was a significant advantage using LPV/r over ATV+RTV, which varied depending on the country's cost structure and assumptions related to drug efficacy. There was a comparative benefit for experienced patients in quality-adjusted life-months (QALM) of 4.6 (the net gain after subtracting quality-adjusted life-years [QALYs] lost owing to CHD risk). In addition, there were 5- and 10-year overall cost savings of between euro947 and euro6594 per patient after 5 years, and an impact ranging from a cost increase of euro308 (for France) to a cost saving of euro7388 (for Spain) at year 10. The lifetime incremental cost-effectiveness ratios ranged from dominant for Spain to euro11 856/QALY for Italy. CONCLUSION LPV/r was a highly cost-effective regimen relative to ATV+RTV for the treatment of HIV for each of the four countries examined in this study. The effect of LPV/r on long-term CHD risk was minimal compared with the increased risk of AIDS/death projected for a less efficacious PI-based regimen. The cost of lipid-lowering drugs and treatment for CHD was insignificant compared with the overall cost savings from LPV/r therapy. The choice of regimen for antiretroviral-experienced patients should be based on a regimen's expected efficacy and durability for countries with similar cost structure to those examined here.