This study compared the cost-efficacy ratios of lopinavir/ritonavir monotherapy (LPV/r-MT) and of standard of care in virologically suppressed HIV-infected patients. The results of the efficacy and safety analyses are presented. We conducted a multicentre, randomised, open-label trial of HIV-infected adults on stable treatment, with HIV- RNA <50 copies/mL, randomised to continue the ongoing regimen (cART-arm) or to switch to LPV/r (400/100 mg BID) MT (MT-arm). Time to virological rebound (VR = confirmed HIV-RNA ?50 copies/mL) was estimated by Ka- plan-Meier method and changes in laboratory values during follow-up were evaluated by univariate mixed-linear models. Ninety-four patients were randomised and analysed (43 in the MT-arm and 51 in the cART-arm). Five (four in the MT and 1 in the cART-arm; p=0.175) had VR, but time to VR did not statistically differ between the two arms (p=0.143). Major PI mutations were not detected at VR. Patients on MT had significant increases in total choles- terol [difference in mean change between MT and cART arm: 0.77 (±0.30) mg/dL per month; p=0.012] and eGFR [difference in mean change between MT and cART arm: 0.24 (±0.11) mL/min/1.73 m2 per month; p=0.029]. LPV/r-MT seems safe in most patients and should be considered in patients who have developed kidney toxicity from tenofovir.