The essential oils of Ocimum ciliatum Hornem, Ocimum basilicum var. purpurascens Benth, Ocimum basilicum var. dianatnejadii Salimi and Ocimum minimum L. from aerial parts of plants grown in Iran were obtained by hydro-distillation and examined by gas chromatography (GC) and GCâmass spectrometry (GCâMS). In total, twenty-eight, thirty-two, twenty-five and thirty-four constituents were identified and quantified in O. ciliatum, O. basilicum var. purpurascens, O. basilicum var. dianatnejadii and O. minimum, representing 93.9â98.5% of the total oils, respectively. Methyl chavicol (30.3%), geranial (23.0%), neral (16.8%) and methyl eugenol (5%) were the major components in the oil of O. ciliatum. Methyl chavicol (43.0%) and linalool (28.9%) were identified as the major compounds in the oil of O. basilicum var. purpurascens, while methyl chavicol (37.6%), linalool (33.4%) and Î±-cadinol (5.7%) were the major constituents in the oil of O. basilicum var. dianatnejadii. The essential oil of O. minimum was rich geranyl acetate (45.6%) and linalool (25.6%).