The essential oils of basil (Ocimum minimum L.) leaves cultivated in Mersin (Büyükeceli-Gülnar) were extracted by hydrodistillation, and analysed by GC and GC-MS. The major constituents varied depending on harvest years. Linalool, eucalyptol, eugenol and epi-α-cadinol were determined as the major components of basil leaves collected between 2003 to 2008 years. The main constituents of oil were linalool (40.2 2% to 88.34%), eucalyptol (1.46% to 8.87%), eugenol (0.28% to 7.23%) and epi-α-cadinol (1.35% to 5.05%) depending on years. The essential oil composition varies qualitatively and/or quantitatively with the time of harvest.