A method of treating HIV infection in a human patient wherein the infecting HIV strain has become resistant to atazanavir, the method comprising administration of a therapeutically effective amount of a combination of atazanavir or a pharmaceutically acceptable salt thereof, and at least one other HIV protease inhibitor. A method for enhancing the effectiveness of a second HIV protease inhibitor in treating HIV infection in a human patient whose HIV strain has become resistant to atazanavir or a pharmaceutically acceptable salt thereof, comprising administering to said human patient an amount of atazanavir or a pharmaceutically acceptable salt thereof effective in maintaining the resistant strain, in combination with the second HIV protease inhibitor. The resistance to atazanavir in the human is manifested by the existence of the signature mutation consisting of I50L mutation in the HIV protease.