The combination of the HIV protease inhibitor Compound A and one or more nucleoside reverse transcriptase inhibitors, non-nucleoside reverse transcriptase inhibitors, or protease inhibitors is useful in the inhibition of HIV protease, the inhibition of HIV reverse transcriptase, the prevention or treatment of AIDS, either as compounds, pharmaceutically acceptable salts or esters, pharmaceutical composition ingredients, whether or not in combination with other antivirals, immunomodulators, antibiotics or vaccines. Methods of treating AIDS and methods of preventing or treating infection by HIV are also described.