Objectives: To study the pharmacokinetics and short-term efficacy of low and standard dose lopinavir/ritonavir and saquinavir combinations in Thai, human immunodeficiency virus (HIV)-infected, treatment-naive patients. Methods: In this open-label, 24-week, prospective study, 48 treatment-naive patients were randomized to lopinavir/ritonavir 400/100 mg + saquinavir 1000 mg twice daily (arm A), lopinavir/ritonavir 400/100 mg + saquinavir 600 mg twice daily (arm B), lopinavir/ritonavir 266/66 mg + saquinavir 1000 mg twice daily (arm C), or lopinavir/ritonavir 266/ 66 mg + saquinavir 600 mg twice daily (arm D). A 12 h. pharmacokinetic profile in all patients was performed. Plasma concentrations of saquinavir and lopinavir were determined using an HPLC technique. HIV-1 RNA was measured over 24 weeks. Results: Forty-three subjects were included in the pharmacokinetic analysis. The total exposure differed significantly for the different arms. Median values for lopinavir area under the curve at 0-12 h were 128.2, 119.2, 66.1 and 68.5 mg·h/L for arms A - D, respectively. For saquinavir, the median values were 36.9, 19.2, 25.3 and 12.4 mg·h/L for arms A - D, respectively. The proportion of patients having a viral load below 50 copies/mL at week 24 was 39% for arm A, 63% for arm B, 55.0% for arm C, and 69% for arm D. Conclusions: The pharmacokinetic parameters for the different treatment arms were adequate. However, the proportion of subjects with an undectable viral load at week 24 was lower than anticipated.