The purpose of this study is to describe long term (> 96 weeks) efficacy and safety of Atazanavir-based regimens in real life setting.

Time perspective: Collection of historical data and longitudinal follow up. Patients will be enrolled in 2011/2012 but data will be collected from medical charts from ATV initiation date (Feb 2008 - July 2010) until July 2013 at the latest (if no ATV discontinuation, or death, or lost to follow up).

Non probability sample:

• Specialized HIV management centers will be contacted in order to recruit about 15-20 sites per country.
• Each site will have to enroll an average of 8-12 consecutive patients (min:5; max:30) fulfilling the inclusion/exclusion criteria.

Inclusion Criteria:

• Male or Female HIV patients ≥ 18 years old at ATV/RTV initiation treatment date
• Outpatient seen in routine consultation whatever the reason, between January 1st 2011 and March 31st 2012
• Commencing an ATV/RTV-based regimen including at least 2 nucleoside reverse transcriptase inhibitors (NRTI) after February 1st 2008 and before July 31st 2010, regardless of the current ARV treatment ongoing at enrollment visit

Exclusion Criteria:

• Patient exposed to or who began ATV/RTV prior to February 1st 2008, or after July 31st 2010 or without a known start date for ATV/RTV therapy
• Exposure to more than 4 weeks of any ARV prior to initiation of ATV/RTV treatment
• Participation in a clinical trial with ATV at the time of or after initiation of ATV/RTV-based regimen

Patients attending HIV specialized management centers will be considered.