abstract the samples of an interspecific hybrid of thyme, thymus x oblongifolius opiz, were collected at four habitats in lithuania. the compositions of their essential oils were analyzed by capillary gas chromatography (gc) and mass spectrometry (ms). the oil of the hybrid showed an intermediate composition compared with those of the parent species-t. serpyllum l. and t. pulegioides l. two samples contained thymol (1.0% and 6.7%) and carvacrol (0.6% and 13.6%). these constituents are characteristic for the thymol/carvacrol chemotype of t. pulegioides growing in lithuania. other important constituents in the hybrid were 1, 8-cineole (up to 14.7%) and camphor (up to 4.7%). considerable amounts of these compounds were determined in t. serpyllum. one t. x oblongifolius sample was rich in germacrene b (24.4%). key word index: thymus oblongifolius lamiaceaeessential oil compositionthymolcarvacrolgermacrene b1,8-cineole