The study aims to describe the changes of combination antiretroviral therapy and the causes that motivated them.

Inclusion Criteria:

• Patients older than 18 years
• Patients with HIV
• Patients in antiretroviral regimen, that have changed the antirretroviral treatment.

Exclusion Criteria:

• Patients unable to sign the consent form
• patients that changing their treatment are going to take the same components in co-formulated
• patients that changing their treatment are going to take the same components separately
• Total or selective interrupts not indicated by the specialist
• Patients that after changing antiretroviral therapy between January 2011 and July 2012, and during the next year, again suffered another change of treatment

HIV patients that have changed antirretroviral régimen between Jan 2011 and Jul 2012