A large sample of fresh basil, Ocimum basilicum L., was dried at 45°C for 12 hours and stored. After three, six and seven months, qualitative and quantitative analyses of the essential oil were performed by steam distillation and GC-MS. The principal components found in the essential oils were: methylchavicol, eugenol, linalol and 1,8-cineole: the content of methylchavicol and eugenol decreased drastically after drying and storage, while that of linalol and 1,8 cineole increased over the same period. The losses of total essential oil after drying were 19%, 62% and 66% at three, six and seven months storage respectively. Several types of reaction seemed to take place during drying and storage.