the essential oil from the aerial parts of two cultivated subspecies from porophyllum ruderale, porophyllum ruderale subsp. macrocephalum (prm) and porophyllum ruderale subsp. ruderale (prr) were obtained by hydrodistillation and analyzed by gas chromatography (gc) and gc-mass spectrometry (gc-ms). monoterpenes were the most abundant components. the oil from prm presented limonene (83.5%), myrcene (6.3%) and 1-undecene (5.4%) as the major compounds, while the oil from prr contained e--ocimene (54.9%), limonene (25.2%) and -pinene (10.1%) as the main components. these results suggest that the main component of the essential oil can differentiate the two p. ruderale subspecies.