Two field experiments were carried out during two summer successive seasons of 2004 and 2005 at the Experimental Station of the Medicinal and Aromatic Plants, Fac. Agric., Mansoura Univ. to evaluate the effect of phosphorus fertilizer levels (0, 15.5, 23.25, and 31 kg P₂O₅ / fed) with or without bio-fertilizers (VA-Mycorrhizae and phosphorein) on vegetative growth, herb yield and essential oil content as well as mineral elements (N, P and K) of marjoram plant.    Data revealed that plants treated with phosphorus recorded considerable increments with regard to growth characters, herb yield, essential oil content, components and mineral elements. The best results in this concern were obtained by using the highest level of phosphorus (31kg P₂O₅ / fed).  Also, obtained data showed that bio-fertilizers (VA-Mycorrhizae and phosphorein) improved the growth characters expressed as plant height, number of branches, plant fresh and dry weight, herb yield, essential oil content and mineral elements compared with control. The interaction between mineral and bio-phosphate improved plant growth which gave higher herb yield, essential oil content and mineral elements resulted from Mycorrhizae treatment with 23.25 or 31 kg P₂O₅ / fed, compared with other treatments. The highest values resulted from Mycorrhizae with 31 kg P₂O₅ / fed treatment plants.