Abstract Essential oils from the aerial parts of Sicilian Teucrium flavum L., isolated by using microwave-assisted hydrodistillation (MHD), were analyzed for the first time at various seasonal stages (vegetative and budding stage) by means of GC/MS and GC-FID; the flowers and fruits were also subjected to examination. More than 80 compounds were identified as oil components. The leaf, flower and fruit oils were characterized by a predominance of sesquiterpenes, such as Î²-ryophyllene (3â5 g/100 g), germacrene D (4â14 g/100 g), Î²-bisabolene (32â49 g/100 g); the total amount of sesquiterpene hydrocarbons contained in each oil was 56â70 g/100 g, the oxygenated derivatives were in the range of 9â20 g/100 g. The monoterpene hydrocarbons in all samples (leaves, flowers, fruits) were contained in very low amounts, from 0.2 to 1.6 g/100 g, and were the least representative fraction of the oils. Oxygenated aliphatic compounds, especially esters, were also detected. The results can be useful to support, by means of a safe reliable sample preparation (MHD) and analytical (GC) technique, the research on medicinal plants belonging to Mediterranean flora.