Inclusion Criteria:

1. The patients must fulfill all of the following criteria: The patient has confirmed his/her willingness to participate in the study, after being informed about all the aspects of the study that might be relevant for his/her decision to participate, and has signed and dated the informed consent form, as approved by the Institutional Review Board/ Ethics Committee (IRB/EC). And he/she can withdraw the study participation at any moment, if he/she wants to do so.
2. The patient has laboratorial confirmation of an HIV infection through a positive ELISA test for anti-HIV antibodies and an additional test (Western-blot, indirect immunofluorescence or PCR).
3. The patient must be in treatment with at least three antiretroviral drugs, for at least 6 months without changes.
4. The patient should have no history of documented virological failure to previously used antiretroviral therapies.
5. Undetectable viral load (test result < 400 copies/ml) for more than 6 months measured on a sample collected during treatment with the current regimen and at screening (test result < 80 copies).
6. CD4 count > 200 cels/ml at screening
7. Patient agrees not to use concomitant medication that might have unacceptable drug interactions with the study drug.
8. If the patient is a female, she must have a negative pregnancy test and must agree to use at least 14 days before the study drug administration and for the whole study duration and up to 6 months after, a barrier contraceptive method with a proven reliability track record, as judged by the investigator

Exclusion Criteria:

1. Pregnant or lactating female patient. If the patient becomes pregnant during the study, she will be discontinued from the study.
2. Patients with allergic reaction or hypersensitivity to Lopinavir or Ritonavir .
3. A patient with previous history of opportunistic disease ( appendix 1) or CD4 count below 100 cels/mm3.
4. A patient who presents any HIV viral load test result above 400 copies/mL over the past 6 months.
5. Patient who is receiving or has received systemic chemotherapy during the past 6 months.
6. Laboratory test results Hemoglobin < 8 g/dl Absolute neutrophil count < 750 cels/mL Platelet count < 20,000/mL Bilirubin > 1.5 x UNL or > 6 x UNL if patient is using Indinavir or Atazanavir ALT and AST > 2 x UNL Creatinine > 2 x UNL
7. Patient is taking any drug known to be contraindicated concomitantly with lopinavir/r. Please refer to the product’s package insert.
8. According to the investigator’s opinion, the patient has little probability of complying with the study protocol or is unsuitable for any other reason.