Green friable calli (G-calli) and dark abnormal root primordia containing calli (R-calli) of Origanum vulgare ssp. virens were induced from leaves and established in the presence of 0.25 mg and I mg l(-1) (2,4-D), respectively. Leaves, of the same type of those used in the calli induction, G-calli and R-calli were submitted to hydrodistillation and the respective hydrodistillates were analysed by GC and GC-mass spectrometry. The hydrodistillate from leaves consisted of ca 50% monoterpenoids (35.2% oxygenated monoterpenes and 14.3% monoterpene hydrocarbons) and ca 40% of sesquiterpenoids (2.5% oxygenated sesquiterpenes and 37.4% sesquiterpene hydrocarbons). Linalool(16.4%) and (E)-beta-ocimene (6.6%) were the major oxygenated monoterpene and monoterpene hydrocarbon, respectively. Globulol (0.94%) and delta-elemene (12;85%) were the major oxygenated sesquiterpene and sesquiterpene hydrocarbon, respectively, n-Alkanes, namely pentacosane (0.97%), heptacosane-(0.9%) and nonacosane (1.0%), were also present. Hydrodistillates from G- and R-calli did not contain either mono- or sesquiterpenoids; n-alkanes were the main compounds found. The alkane concentration in R-calli was more than twice that of G-calli. Naphthalene (0.5 mu g g(-1) dry wt)and eicosane, (0.9 mu g g(-1) dry wt) produced by R-calli were absent in G-calli. Squalene concentration in G-calli was 6.7 fold greater than that found in R-calli. (C) 1998 Elsevier Science Ltd. All rights reserved.