Abstract Three chemotypes of Thymus longicaulis C. Presl subsp. chaoubardii (Reichenb. fil.) Jalas were collected from the same population growing in one m2 area. Their oils were examined by GC and GC/MS. Limonene (18.7%) and thymol (19â4%); geraniol (56.8%) and geranyl acetate (7.6%); linalool (63.1%) and α-terpinyl acetate (20.4%) were the predominant components in each of the three different chemotypes, respectively. The oils also exhibited moderate to strong antimicrobial activity against the six Gram (±) tested bacteria