No differences in viral load (VL) or CD4+ count at 48 weeks were reported for the CASTLE study. However, total cholesterol (TC) levels were elevated in 7% and 18% of subjects receiving ATV+RTV and LPV/r, respectively. These measures can predict outcomes which affect the future cost of HIV in the Swedish health system. OBJECTIVES: To compare the incremental cost effectiveness (ICER) and budget impacts for a population similar to those enrolled in the CASTLE study for Sweden. METHODS: Using a previously published Markov model of HIV disease and 2009 cost data from Sweden, we compared the cost/QALY and budget impact of the two ARV regimens. Daily drug costs were 160,52 SEK for ATV+RTV and 147,87SEK for LPV/r. Costing for other health care resources used a health systems perspective with 2009 inputs from www.fass.se and published literature. Costs and QALYs were discounted by 3% when calculating ICERs. RESULTS: The CHD risk favored ATV+RTV, resulting in a life expectancy increase of 0.031 QALYs (11 days).  The cost effectiveness ratio for ATV+RTV for Sweden was 1.251.545 SEK /QALY gained. Three times the Swedish GDP in 2008 was 886,670 SEK. Thus the modeled ICER exceeds the WHO criteria for cost effectiveness by 40%.  Sensitivity analysis showed the model was mainly sensitive to ARV price. Five and 10 years per-patient savings for subjects on the LPV/r regimen were estimated to be 21,314 SEK and 32,564 SEK, respectively. CONCLUSIONS: Selection of an ATV+RTV based regimen in an ARV-naïve population with a CHD risk similar to subjects in the CASTLE study does not appear to be a cost effective use of scarce resources for the cost structure seen in Sweden. The costs associated with the very small added CHD risk incurred by LPV/r treatment are more than offset by its short and long term cost savings.