The essential oil from the rhizomes of Piper betle L. (betel), collected around Hue, was obtained in 0.20% yield. The oil was examined by a combination of capillary GC and GC/MS. 13C-NMR studies confirmed the structure assignments proposed by retention data and mass spectra of the components with a content higher than 1%. In some instances the structure elucidation based on GC and GC/MS data had to be corrected. More than forty constituents were found of which the major ones were \alpha-cadinol (26.2%), \delta-cadinene (11.7%), and about equal amounts of T-cadinol and T-muurolol (unseparated, together 20.7%). This study clearly illustrates the advantage of complementary identification techniques.