Essential oil (EO) was extracted using hydrodistillation from samples of Origanum vulgare subspecies hirtum (Link) Ietswaart, gathered from the wild in various parts of Sicily, Italy; GC-FID and GC-MS analyses were subsequently performed. The aim of the study was to analyze the relationship between essential oil yields and the geographical distribution of oregano wild populations based on variations in environmental factors as collection sites. Moreover, the purpose was to group Origanum vulgare subspecies hirtum biotypes according to the chemical composition of the EO. The seven principal components in the EO was thymol (24.0â54.4%), Î³-terpinene (9.8â30.5%), Ï-cymene (5.2â18.7%), Î±-terpinene (2.7â5.7%), carvacrol (0.3â8.3%), terpinen-4-ol (0.5â9.4%) and trans-sabinene hydrate (0.0â12.8%). All the biotypes analyzed were identified as thymol-chemotype. Statistical analysis shows that essential oil yields are mostly affected by weather/climate and topographic characteristics of the collection sites.