The HIV-inhibitory activity in extracts of Allanblackia stuhlmannii was tracked, via bioassay-guided fractionation, to a new member of the camboginol/guttiferone class of prenylated benzophenones, guttiferone F (1). The structure was solved by extensive NMR analyses and by acid-catalyzed conversion to 30-epi-cambogin (4). This is the first report of this compound type in the genus Allanblackia.