Water and methanol extracts ofRosa damascenaexhibited moderate anti-HIV activity. The anti-viral activities of 9 compounds isolated from the methanol extract were compared. The tetrahydroxyflavanone (kaempferol,1), was effective in reducing the maturation of infectious progeny virus apparently due to selective inhibition of the viral protease. On the other hand the pentahydroxyflavone (quercetin,2) and two3-substituted derivatives of kaempferol appeared to inhibit HIV-infection by preventing binding of gp120 to CD4. 2-Phenylethanol-O-(6-O-galloyl)-β-D-glucopyranoside8interacted irreversibly with gp120 and neutralized virus infectivity. The differences in the modes of action of1and8can account for the apparent synergy of their anti-viral activities.