This work investigates the influence of water stress on vegetative growth, essential oil, proline, total carbohydrates, N, P, K, and protein contents of two species of an herb plant ie Ocimum basilicum L. (sweet basil) and Ocimum americanum L. (american basil). Experiments were carried out during two successive seasons, 2004 and 2005, with experimental pots containing Typic Torrifluvents soil (a clay loam) in a growth chamber at the Experimental Farm, National Research Center (NRC), Giza, Egypt. Seedlings were treated with different levels of water-stress, determined as a percentage of field water capacity (FWC) by weight (50, 75, 100, and 125%). Fresh and dry weights of the herbs were significantly influenced by water stress. For both species under water stress, essential oil percentage, the main constituents of essential oil, proline, and total carbohydrate content increased, and N, P, K, and protein content decreased. Seventy five percent field water capacity resulted in the highest yield of herb and essential oil for both species.