Lipophilic fractions of stem extracts from Exocarpos latifolius, native to Papua New Guinea, showed significant activity against Mycobacterium tuberculosis H37Ra. Bioactivity-guided fractionation yielded exocarpic acid (E-octadeca-13-ene-9,11-diynoic-acid) as the major active component. Several new exocarpic acid analogs were also shown to be active. Exocarpic acid has previously been reported active against gram-positive, but not gram-negative bacteria. Work presented here demonstrates the selective activity of exocarpic acid against Mycobacterium tuberculosis H37Ra.