The leaf oil of Heteropyxis dehniae Suess. (Heteropyxidaceae) was obtained by hydrodistillation and analyzed by GC/MS. The most abundant essential oil components are linalool (58.3%), 4-terpineol (9.8%), α-terpineol (3.6%), and caryophyllene oxide (3.1%). The antimicrobial activity against Bacillus cereus, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Candida albicans, and Aspergillus niger, and the in vitro cytotoxicity of the oil on PC-3, MDA-MB-231, Hs 578T, MCF7, SK-MEL-28, and 5637 human tumor cells were also examined. Caryophyllene oxide shows notable cytotoxic activity with LC 5 0 values of 147-351μM.