Sweet bash (Ocimum basilicum L.) is one of the most popular fresh herbs. Ocimum basilicum shows great variation in morphology and essential oil components. This study was conducted to determine essential oil yields and components of different basil cultivars when grown in the Mediterranean region of Turkey. Seeds of four cultivars of sweet basil were provided from Greece, France, Germany, and Turkey. Basil plants were allowed to flower three times during the summer period. Essential oils were extracted from flowering plants by hydrodistillation, and the oil was analyzed by GC and GC/MS. Essential oil ratio and components showed great variation, depending on the cultivars and harvest times. The results showed the existence of three different chemotypes according to main compounds: Linalool (Greek basil), linalool+methylcinnamate (Turkish and German basil), and linalool+methyl eugenol (French basil).