[en] Background: Trachylobane diterpenes are secondary metabolites quite rare in nature and their bioactivities are poorly known. Recently we have described the cytotoxic activity of ent- trachyloban-3‚-ol isolated from the leaves of Croton zambesicus, a plant used in African folk medicine. Materials and Methods: Cell viability on several cell lines, cell morphology, DNA laddering, annexin V and caspase-3 activation experiments were undertaken in order to analyse the cytotoxicty of trachylobane diterpene and to determine if this compound is able to induce apoptosis. Results: ent-trachyloban-3‚-ol exerts a dose-dependent cytotoxic effect and which varies between cell lines. Induction of apoptosis in HL-60 cells could be detected at a concentration of 50 ÌM after 24-h treatment. Conclusion: We show here, for the first time, that a trachylobane diterpene is able to induce apoptosis in human promyelocytic leukemia cells via caspase-3 activation in a concentration-dependent manner.