The leaf essential oil of Croton flavens L., a native plant from the Caribbean area used in traditional medicine, was extracted by hydrodistillation. The composition of the volatile fraction of this essential oil was determined by GC and GC-MS analyses. We have identified 47 compounds, of which viridiflorene (12.22%), germacrone (5.27%), (E)-gamma-bisabolene (5.25%) and beta-caryophyllene (4.95%) are the main components. The anticancer activity of this extract was tested on human lung carcinoma cell line A-549 and human colon adenocarcinoma cell line DLD-1. Croton flavens leaf essential oil was found to be very active against both tumor cell lines, with a GI(50) of 27 +/- 4 microg/ml for A-549 and 28 +/- 3 microg/ml for DLD-1. Three compounds identified in the leaf essential oil, alpha-cadinol (3.97%), beta-elemene (1.53%) and alpha-humulene (1.06%) are cytotoxic against tumor cell lines.