The leaves of Croton zambesicus are widely used in African folk medicine as a water decoction to treat hypertension, microbial infections and fever associated with malaria. Cytotoxic trachylobane and pimarane diterpenes have been isolated from a dichloromethane extract of the leaves. In order to check whether these compounds are present in the essential oil, we have analysed its composition by GC-FID and GC–MS. The major constituents of the oil are caryophyllene oxide (19.5%), β-caryophyllene (10.8%), α-copaene (6.3%), linalool (6.1%) and β-pinene (5.2%). Only the less polar diterpenes are present in the oil: ent-trachyloban-3-one (3.0%), ent-trachyloban-3β-ol (0.5%), isopamara-7, 15-dien-3β-ol (1.0%), ent-trachylobane (0.7%), sandaracopimaradiene (0.4%) and kaurene (2.1%). Copyright © 2005 John Wiley & Sons, Ltd.