the peel's essential oil of the tunisian citrus sinensis (l.) osbeck var 'maltaise demi sanguine' cultivated in six regions and three bioclimatic stages was analyzed by gas chromatography. essential oil yields were highly affected by the growing region and stage. the highest oil yield was observed at sub-humid stage: 1.41% in oued-mliz, 0.95% in bizerte and 0.84% in takelsa and the weakest yield percentage of 0.71% was found in kairouan characterized by an arid superior stage. the main components limonene, linalool, -terpineol, 4-terpineol and -myrcene showed significant variations in dry region. principal component analysis and hierarchical clustering of composition revealed high effect of the bioclimatic stage, the coastal location and the altitude. besides this, the results of this investigation provided a preliminary evidence for specific markers to each region that could constitute a useful tool in the quality control and the determination of the botanical origin of the oils.