To evaluate the proportion of patients with virological failure after 48 weeks of treatment with the combination of efavirenz 600 mg + lamivudine (3TC) 300 mg + abacavir 600 mg once daily as an antiretroviral simplification regimen.

Treatment simplification is a therapeutic strategy that allows patients with controlled viral replication to switch to an easier-to-take antiretroviral system to promote long-term adherence and thus maintain controlled viral load for longer, delaying the evolution of the HIV infection.

The combination of ABC+3TC+EFV is a potent and easy-to-take regimen (2 tablets once a day) that could be suitable for the simplification of antiretroviral treatment in patients with controlled viral load with a regimen that includes 2 NRTI taken twice daily.

Inclusion Criteria:

1. Age > 18 years.
2. HIV-1 infected patients.
3. Patients on HAART therapy including efavirenz and two NRTIs in a twice-daily regimen for 6 months at least.
4. Patients with an undetectable HIV-1 viral load over the last 6 months (at least 2 determinations separated by 3 months).
5. Subject able to follow the treatment period.
6. Signature of the informed consent.
7. Women may not be of fertile age (defined as at least one year from menopause or undergoing any surgical sterilisation technique), or must undertake to use a barrier contraceptive method during the study.

Exclusion Criteria:

1. Hepatic tests > 5 times above normality.
2. Pregnancy or breastfeeding
3. Presence of opportunistic infections and/or recent tumours (< 6 months).
4. Suspected or documented resistance to any of the investigational drugs.
5. Known allergic hypersensitivity to any of the investigational drugs or any similar drug.
6. Subjects with abusive consumption of alcohol or illegal drugs.
7. Patients participating in another clinical trial.