The use of the hemifumarate form of {9-[(R)-2-[[(S)-[[(S)-1-(isopropoxycarbonyl)ethyl]amino]phenoxyphosphinyl]methoxy]propyl]adenine} (tenofovir alafenamide hemifumarate) in combination with cobicistat is disclosed. In addition, the combination of tenofovir alafenamide hemifumarate, cobicistat, emtricitabine, and elvitegravir, and the combination of tenofovir alafenamide hemifumarate, cobicistat, emtricitabine, and darunavir, are disclosed.