The antibacterial activity of 13-epi-sclareol, a labdane type diterpene, isolated from the resinous exudate of Pseudognaphalium heterotrichium and P. cheiranthifolium was tested against four Gram positive and three Gram negative bacteria. The antimicrobial activity was determined using three different methods: solid medium, liquid medium and a liquid medium micro-method. The bacterial viability and growth curve were also studied. Gram positive bacteria were selectively affected by 13-epi-sclareol. At concentrations of 30 µg/mL, the compound produced the lysis of Bacillus cereus and B. subtilis.