[en] Ocimum basilicum essential oil (Algerian species), which is extracted from dried leaves with an output of 1.98 ± 0.01%, is yellow pale. Its chemical composition has been investigated by GC/MS and GC/FID. Fourty compounds have been identified accounting for 97.4%. The major compounds were: Linalool (32.83%), linalyl acetate (16%), elemol (7.44%), geranyl acetate (6.18%), myrcene (6.12%), allo-ocimene (5.02%), α-terpineol (4.9%), (E)-β-ocimene (3.68%) and neryl acetate (3.45%). O. basilicum essential oil was screened for its in vitro antioxidant activity using DPPH assay. The results showed that the concentration of the essential oil needed to scavenge 50% of DPPH, was 83.54 mg/ml lower than that of vitamin E (22.0 mg/ml) and therefore acts as a natural antioxidant agent.