Bioactivity-guided fractionation of the hexane extract of the stems and leaves of Hypericum drummondii has afforded four new filicinic acid derivatives: drummondin D, isodrummondin D, drummondin E, and drummondin F. The structures of these compounds were established by spectroscopic methods. All compounds possessed strong antibiotic activity against the Gram-positive bacteria Staphylococcus aureus and Bacillus subtilis and the acid fast bacterium Mycobacterium smegmatis.