(−)-Guaiol is a sesquiterpene alcohol that has been found in several traditional Chinese medicinal plants and has antiproliferative, pro-autophagic, insect repellent, and insecticidal biological activities.^1,2,3 It selectively inhibits proliferation of A549 and H1299 non-small cell lung carcinoma (NSCLC) cells over BEAS-2B normal lung cells (IC50s = 121.7, 211.5, and 297.1 μM, respectively).¹ It also dose-dependently induces formation of DNA double-strand breaks (DSBs) and autophagy in A549 and H1299 cells and increases levels of microtubule-associated protein 1 light chain 3 isoform II (LC3-II). (−)-Guaiol (8 mg/kg three times per week) inhibits tumor growth in an NSCLC mouse xenograft model. It deters A. aegypti and A. quadrimaculatus mosquitoes from feeding on a synthetic blood substitute with a biting-deterrent index (BDI) of 0.82 when used at a concentration of 25 nmol per cm2.2 (−)-Guaiol is also lethal to fourth instar M. separata and third instar P. xylostella larvae (LD50s = 0.07 and 8.9 mg/larva, respectively).³