Inclusion Criteria:

• HIV-infected as documented by positive HIV antibody test and confirmed by Western Blot.
• Subject is at least 18 years of age at the day of screening.
• Subject is able and willing to sign the Informed Consent Form prior to screening evaluations.
• HIV-1 RNA < 40 copies/mL for at least 6 months on antiretroviral therapy.
• Subject has no history of previous virological failure or documented resistance mutations

Exclusion Criteria:

• History of sensitivity/idiosyncrasy to the drug or chemically related compounds or excipients, which may be employed in the trial.
• Relevant history or current condition that might interfere with drug absorption, distribution, metabolism or excretion.
• Inability to understand the nature and extent of the trial and the procedures required.
• Pregnant female (as confirmed by an HCG test performed less than 3 weeks before the first dose) or breast-feeding female.
• Abnormal serum transaminases determined as levels being > 5 times upper limit of normal (see Appendix A for normal ranges of clinical laboratory values).
• Concomitant use of medications that interfere with raltegravir or atazanavir pharmacokinetics: rifampicin, irinotecan, midazolam, triazolam, ergotamine, dihydroergotamine, cisapride, pimozide, lovastatin, simvastatin, indinavir, proton pump inhibitors, H2 receptor antagonists, St. john's wort, Ginkgo Biloba, didanosine, tenofovir, efavirenz, nevirapine, antacids, clarithromycin, phenytoin, phenobarbital, carbamazepine.
• Active hepatobiliary or hepatic disease (including chronic hepatitis B infection).
• Alcohol abuse.